Systems and Methods of RF Power Transmission, Modulation and Amplification

ABSTRACT

Methods and systems for vector combining power amplification are disclosed herein. In one embodiment, a plurality of signals are individually amplified, then summed to form a desired time-varying complex envelope signal. Phase and/or frequency characteristics of one or more of the signals are controlled to provide the desired phase, frequency, and/or amplitude characteristics of the desired time-varying complex envelope signal. In another embodiment, a time-varying complex envelope signal is decomposed into a plurality of constant envelope constituent signals. The constituent signals are amplified equally or substantially equally, and then summed to construct an amplified version of the original time-varying envelope signal. Embodiments also perform frequency up-conversion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 13/532,968, filed on Jun. 26, 2012, which is a continuation ofU.S. Pat. No. 8,334,722, filed Jun. 30, 2008, claiming the benefit ofU.S. Provisional Patent Application No. 60/929,450, filed Jun. 28, 2007,and U.S. Provisional Patent Application No. 60/929,585, filed Jul. 3,2007, all of which are incorporated herein by reference in theirentireties. The present application is related to U.S. patentapplication Ser. No. 11/256,172, filed Oct. 24, 2005, now U.S. Pat. No.7,184,723 and U.S. patent application Ser. No. 11/508,989 filed Aug. 24,2006, both of which are incorporated herein by reference in theirentireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to RF power transmission,modulation, and amplification. More particularly, the invention relatesto methods and systems for vector combining power amplification.

2. Background Art

In power amplifiers, a complex tradeoff typically exists betweenlinearity and power efficiency.

Linearity is determined by a power amplifier's operating range on acharacteristic curve that relates its input to output variables—the morelinear the operating range the more linear the power amplifier is saidto be. Linearity is a desired characteristic of a power amplifier. Inone aspect, for example, it is desired that a power amplifier uniformlyamplifies signals of varying amplitude, and/or phase and/or frequency.Accordingly, linearity is an important determiner of the output signalquality of a power amplifier.

Power efficiency can be calculated using the relationship of the totalpower delivered to a load divided by the total power supplied to theamplifier. For an ideal amplifier, power efficiency is 100%. Typically,power amplifiers are divided into classes which determine theamplifier's maximum theoretical power efficiency. Power efficiency isclearly a desired characteristic of a power amplifier—particularly, inwireless communication systems where power consumption is significantlydominated by the power amplifier.

Unfortunately, the traditional tradeoff between linearity and efficiencyin power amplifiers is such that the more linear a power amplifier isthe less power efficient it is. For example, the most linear amplifieris biased for class A operation, which is the least efficient class ofamplifiers. On the other hand, higher class amplifiers such as class B,C, D, E, etc, are more power efficient, but are considerably non-linearwhich can result in spectrally distorted output signals.

The tradeoff described above is further accentuated by typical wirelesscommunication signals. Wireless communication signals, such as OFDM,CDMA, and W-CDMA for example, are generally characterized by theirpeak-to-average power ratios. The larger the signal's peak to averageratio the more non-linear distortion will be produced when non-linearamplifiers are employed.

Outphasing amplification techniques have been proposed for RF amplifierdesigns. In several aspects, however, existing outphasing techniques aredeficient in satisfying complex signal amplification requirements,particularly as defined by wireless communication standards, forexample.

In one aspect, existing outphasing techniques employ an isolating and/ora combining element when combining constant envelope constituents of adesired output signal. For example, it is commonly the case that a powercombiner is used to combine the constituent signals. This combiningapproach, however, typically results in a degradation of output signalpower due to insertion loss and limited bandwidth, and, correspondingly,a decrease in power efficiency.

In another aspect, the typically large size of combining elementsprecludes having them in monolithic amplifier designs.

What is needed therefore are power amplification methods and systemsthat solve the deficiencies of existing power amplifying techniqueswhile maximizing power efficiency and minimizing non-linear distortion.Further, power amplification methods and systems that can be implementedwithout the limitations of traditional power combining circuitry andtechniques are needed.

BRIEF SUMMARY OF THE INVENTION

Embodiments for vector combining power amplification are disclosedherein.

In one embodiment, a plurality of substantially constant envelopesignals are individually amplified, then combined to form a desiredtime-varying complex envelope signal. Phase and/or frequencycharacteristics of one or more of the signals are controlled to providethe desired phase, frequency, and/or amplitude characteristics of thedesired time-varying complex envelope signal.

In another embodiment, a time-varying complex envelope signal isdecomposed into a plurality of substantially constant envelopeconstituent signals. The constituent signals are amplified, and thenre-combined to construct an amplified version of the originaltime-varying envelope signal.

Embodiments of the invention can be practiced with modulated carriersignals and with baseband information and clock signals. Embodiments ofthe invention also achieve frequency up-conversion. Accordingly,embodiments of the invention represent integrated solutions forfrequency up-conversion, amplification, and modulation.

Embodiments of the invention can be implemented with analog and/ordigital controls. The invention can be implemented with analogcomponents or with a combination of analog components and digitalcomponents. In the latter embodiment, digital signal processing can beimplemented in an existing baseband processor for added cost savings.

Additional features and advantages of the invention will be set forth inthe description that follows. Yet further features and advantages willbe apparent to a person skilled in the art based on the description setforth herein or may be learned by practice of the invention. Theadvantages of the invention will be realized and attained by thestructure and methods particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

It is to be understood that both the foregoing summary and the followingdetailed description are exemplary and explanatory and are intended toprovide further explanation of embodiments of the invention as claimed.

BRIEF DESCRIPTION OF THE FIGURES

The application file contains at least one drawing executed in color.Copies of this patent application publication with color drawings willbe provided by the Office upon request and payment of the necessary fee

Embodiments of the present invention will be described with reference tothe accompanying drawings, wherein generally like reference numbersindicate identical or functionally similar elements. Also, generally,the leftmost digit(s) of the reference numbers identify the drawings inwhich the associated elements are first introduced.

FIG. 1A is an example that illustrates the generation of an exemplarytime-varying complex envelope signal.

FIG. 1B is another example that illustrates the generation of anexemplary time-varying complex envelope signal.

FIG. 1C is an example that illustrates the generation of an exemplarytime-varying complex envelope signal from the sum of two or moreconstant envelope signals.

FIG. 1D illustrates the power amplification of an example time-varyingcomplex envelope signal according to an embodiment of the presentinvention.

FIG. 1E is a block diagram that illustrates a vector power amplificationembodiment of the present invention.

FIG. 1 illustrates a phasor representation of a signal.

FIG. 2 illustrates a phasor representation of a time-varying complexenvelope signal.

FIGS. 3A-3C illustrate an example modulation to generate a time-varyingcomplex envelope signal.

FIG. 3D is an example that illustrates constant envelope decompositionof a time-varying envelope signal.

FIG. 4 is a phasor diagram that illustrates a Cartesian 4-Branch VectorPower Amplification (VPA) method of an embodiment of the presentinvention.

FIG. 5 is a block diagram that illustrates an exemplary embodiment ofthe Cartesian 4-Branch VPA method.

FIG. 6 is a process flowchart embodiment for power amplificationaccording to the Cartesian 4-Branch VPA method.

FIG. 7A is a block diagram that illustrates an exemplary embodiment of avector power amplifier for implementing the Cartesian 4-Branch VPAmethod.

FIG. 7B is a block diagram that illustrates another exemplary embodimentof a vector power amplifier for implementing the Cartesian 4-Branch VPAmethod.

FIG. 8A is a block diagram that illustrates another exemplary embodimentof a vector power amplifier according to the Cartesian 4-Branch VPAmethod.

FIG. 8B is a block diagram that illustrates another exemplary embodimentof a vector power amplifier according to the Cartesian 4-Branch VPAmethod.

FIG. 8C is a block diagram that illustrates another exemplary embodimentof a vector power amplifier according to the Cartesian 4-Branch VPAmethod.

FIG. 8D is a block diagram that illustrates another exemplary embodimentof a vector power amplifier according to the Cartesian 4-Branch VPAmethod.

FIGS. 9A-9B are phasor diagrams that illustrate aCartesian-Polar-Cartesian-Polar (CPCP) 2-Branch Vector PowerAmplification (VPA) method of an embodiment of the present invention.

FIG. 10 is a block diagram that illustrates an exemplary embodiment ofthe CPCP 2-Branch VPA method.

FIG. 10A is a block diagram that illustrates another exemplaryembodiment of the CPCP 2-Branch VPA method.

FIG. 11 is a process flowchart embodiment for power amplificationaccording to the CPCP 2-Branch VPA method.

FIG. 12 is a block diagram that illustrates an exemplary embodiment of avector power amplifier for implementing the CPCP 2-Branch VPA method.

FIG. 12A is a block diagram that illustrates another exemplaryembodiment of a vector power amplifier for implementing the CPCP2-Branch VPA method.

FIG. 12B is a block diagram that illustrates another exemplaryembodiment of a vector power amplifier for implementing the CPCP2-Branch VPA method.

FIG. 13 is a block diagram that illustrates another exemplary embodimentof a vector power amplifier for implementing the CPCP 2-Branch VPAmethod.

FIG. 13A is a block diagram that illustrates another exemplaryembodiment of a vector power amplifier for implementing the CPCP2-Branch VPA method.

FIG. 14 is a phasor diagram that illustrates a Direct Cartesian 2-BranchVector Power Amplification (VPA) method of an embodiment of the presentinvention.

FIG. 15 is a block diagram that illustrates an exemplary embodiment ofthe Direct Cartesian 2-Branch VPA method.

FIG. 15A is a block diagram that illustrates another exemplaryembodiment of the Direct Cartesian 2-Branch VPA method.

FIG. 16 is a process flowchart embodiment for power amplificationaccording to the Direct Cartesian 2-Branch VPA method.

FIG. 17 is a block diagram that illustrates an exemplary embodiment of avector power amplifier for implementing the Direct Cartesian 2-BranchVPA method.

FIG. 17A is a block diagram that illustrates another exemplaryembodiment of a vector power amplifier for implementing the DirectCartesian 2-Branch VPA method.

FIG. 17B is a block diagram that illustrates another exemplaryembodiment of a vector power amplifier for implementing the DirectCartesian 2-Branch VPA method.

FIG. 18 is a block diagram that illustrates another exemplary embodimentof a vector power amplifier for implementing the Direct Cartesian2-Branch VPA method.

FIG. 18A is a block diagram that illustrates another exemplaryembodiment of a vector power amplifier for implementing the DirectCartesian 2-Branch VPA method.

FIG. 19 is a process flowchart that illustrates an I and Q transferfunction embodiment according to the Cartesian 4-Branch VPA method.

FIG. 20 is a block diagram that illustrates an exemplary embodiment ofan I and Q transfer function according to the Cartesian 4-Branch VPAmethod.

FIG. 21 is a process flowchart that illustrates an I and Q transferfunction embodiment according to the CPCP 2-Branch VPA method.

FIG. 22 is a block diagram that illustrates an exemplary embodiment ofan I and Q transfer function according to the CPCP 2-Branch VPA method.

FIG. 23 is a process flowchart that illustrates an I and Q transferfunction embodiment according to the Direct Cartesian 2-Branch VPAmethod.

FIG. 24 is a block diagram that illustrates an exemplary embodiment ofan I and Q transfer function according to the Direct Cartesian 2-BranchVPA method.

FIG. 25 is a phasor diagram that illustrates the effect of waveformdistortion on a representation of a signal phasor.

FIG. 26 illustrates magnitude to phase transform functions according toan embodiment of the present invention.

FIG. 27 illustrates exemplary embodiments of biasing circuitry accordingto embodiments of the present invention.

FIG. 28 illustrates a method of combining constant envelope signalsaccording to an embodiment the present invention.

FIG. 29 illustrates a vector power amplifier output stage embodimentaccording to the present invention.

FIG. 30 is a block diagram of a power amplifier (PA) output stageembodiment.

FIG. 31 is a block diagram of another power amplifier (PA) output stageembodiment.

FIG. 32 is a block diagram of another power amplifier (PA) output stageembodiment.

FIG. 33 is a block diagram of another power amplifier (PA) output stageembodiment according to the present invention.

FIG. 34 is a block diagram of another power amplifier (PA) output stageembodiment according to the present invention.

FIG. 35 is a block diagram of another power amplifier (PA) output stageembodiment according to the present invention.

FIG. 36 is a block diagram of another power amplifier (PA) output stageembodiment according to the present invention.

FIG. 37 illustrates an example output signal according to an embodimentof the present invention.

FIG. 38 illustrates an exemplary PA embodiment.

FIG. 39 illustrates an example time-varying complex envelope PA outputsignal and a corresponding envelop signal.

FIG. 40 illustrates example timing diagrams of a PA output stagecurrent.

FIG. 41 illustrates exemplary output stage current control functions.

FIG. 42 is a block diagram of another power amplifier (PA) output stageembodiment.

FIG. 43 illustrates an exemplary PA stage embodiment.

FIG. 44 illustrates an exemplary waved-shaped PA output signal.

FIG. 45 illustrates a power control method.

FIG. 46 illustrates another power control method.

FIG. 47 illustrates an exemplary vector power amplifier embodiment.

FIG. 48 is a process flowchart for implementing output stage currentshaping according to an embodiment of the present invention.

FIG. 49 is a process flowchart for implementing harmonic controlaccording to an embodiment of the present invention.

FIG. 50 is a process flowchart for power amplification according to anembodiment of the present invention.

FIGS. 51A-I illustrate exemplary multiple-input single-output (MISO)output stage embodiments.

FIG. 52 illustrates an exemplary MISO amplifier embodiment.

FIG. 53 illustrates frequency band allocation on lower and upperspectrum bands for various communication standards.

FIGS. 54A-B illustrate feedforward techniques for compensating forerrors.

FIG. 55 illustrates a receiver-based feedback error correctiontechnique.

FIG. 56 illustrates a digital control module embodiment.

FIG. 57 illustrates another digital control module embodiment.

FIG. 58 illustrates another digital control module embodiment.

FIGS. 59A-D illustrate a VPA analog core embodiment.

FIG. 60 illustrates an output stage embodiment according to the VPAanalog core embodiment of FIG. 60.

FIGS. 61A-D illustrate another VPA analog core embodiment.

FIG. 62 illustrates an output stage embodiment according to the VPAanalog core embodiment of FIG. 61.

FIGS. 63A-D illustrate another VPA analog core embodiment.

FIG. 64 illustrates an output stage embodiment according to the VPAanalog core embodiment of FIG. 63.

FIG. 65 illustrates real-time amplifier class control using an exemplarywaveform, according to an embodiment of the present invention.

FIG. 66 is an example plot of output power versus outphasing angle.

FIG. 67 illustrates exemplary power control mechanisms using anexemplary QPSK waveform, according to an embodiment of the presentinvention.

FIG. 68 illustrates real-time amplifier class control using an exemplarywaveform, according to an embodiment of the present invention.

FIG. 69 illustrates real-time amplifier class control using an exemplarywaveform, according to an embodiment of the present invention.

FIG. 70 illustrates an exemplary plot of VPA output stage theoreticalefficiency versus VPA output stage current, according to an embodimentof the present invention.

FIG. 71 illustrates an exemplary VPA according to an embodiment of thepresent invention.

FIG. 72 is a process flowchart that illustrates a method for real-timeamplifier class control in a power amplifier, according to an embodimentof the present invention.

FIG. 73 illustrates an example VPA output stage.

FIG. 74 illustrates an equivalent circuit for amplifier class Soperation of the VPA output stage of FIG. 73.

FIG. 75 illustrates an equivalent circuit for amplifier class Aoperation of the VPA output stage of FIG. 73.

FIG. 76 is a plot that illustrates exemplary magnitude to phase shifttransform functions for amplifier class A and class S operation of theVPA output stage of FIG. 73.

FIG. 77 is a plot that illustrates a spectrum of magnitude to phaseshift transform functions corresponding to a range of amplifier classesof operation of the VPA output stage of FIG. 73.

FIG. 78 illustrates a mathematical derivation of the magnitude to phaseshift transform in the presence of branch phase and amplitude errors.

FIG. 79 illustrates an example MISO power amplifier configuration, whichcan be operated as a Boolean NOR function according to an embodiment ofthe present invention.

FIG. 80 illustrates an example MISO power amplifier configuration, whichcan be operated as a Boolean OR function according to an embodiment ofthe present invention.

FIG. 81 illustrates an example MISO power amplifier configuration, whichcan be operated as a Boolean NAND function according to an embodiment ofthe present invention.

FIG. 82 illustrates an example MISO power amplifier configuration, whichcan be operated as a Boolean AND function according to an embodiment ofthe present invention.

FIG. 83 illustrates an example simulation test bench of a MISO poweramplifier configuration which can be operated to perform a Boolean NORfunction according to an embodiment of the present invention.

FIG. 84 illustrates an example simulation test bench of a MISO poweramplifier configuration which can be operated to perform a Boolean NANDconfiguration according to an embodiment of the present invention.

FIG. 85 illustrates example upper branch and lower branch input signalsprovided to the MISO power amplifier configuration simulated in FIG. 83.

FIG. 86 illustrates example upper branch and lower branch input signalsprovided to the MISO power amplifier configuration simulated in FIG. 84.

FIG. 87 illustrates example output waveforms generated by the MISO poweramplifier configurations simulated in FIGS. 83 and 84.

FIG. 88 illustrates example plots of power output versus outphasingangle for the MISO power amplifier configurations simulated in FIGS. 83and 84.

FIG. 89 illustrates example plots of output current versus outphasingangle for the MISO power amplifier configurations simulated in FIGS. 83and 84.

FIG. 90 illustrates example plots of power output and output currentversus outphasing angle for the MISO power amplifier configurationssimulated in FIGS. 83 and 84.

FIG. 91 illustrates example plots of normalized efficiency versusoutphasing angle for the MISO power amplifier configurations simulatedin FIGS. 83 and 84.

FIG. 92 illustrates an example combined polar-VPA architecture accordingto an embodiment of the present invention.

FIG. 93 illustrates another example combined polar-VPA architectureaccording to an embodiment of the present invention.

FIG. 94 illustrates an example VPA portion of a combined polar-VPAarchitecture according to an embodiment of the present invention.

The present invention will be described with reference to theaccompanying drawings. The drawing in which an element first appears istypically indicated by the leftmost digit(s) in the correspondingreference number.

DETAILED DESCRIPTION OF THE INVENTION Table of Contents 1. Introduction

-   -   1.1. Example Generation of Time-Varying Complex Envelope Input        Signals    -   1.2. Example Generation of Time-Varying Complex Envelope Signals        from Constant Envelope Signals    -   1.3. Vector Power Amplification Overview

2. General Mathematical Overview

-   -   2.1. Phasor Signal Representation    -   2.2. Time-Varying Complex Envelope Signals    -   2.3. Constant Envelope Decomposition of Time-Varying Envelope        Signals

3. Vector Power Amplification (VPA) Methods and Systems

-   -   3.1. Cartesian 4-Branch Vector Power Amplifier    -   3.2. Cartesian-Polar-Cartesian-Polar (CPCP) 2-Branch Vector        Power Amplifier    -   3.3. Direct Cartesian 2-Branch Vector Power Amplifier    -   3.4. I and Q Data to Vector Modulator Transfer Functions        -   3.4.1. Cartesian 4-Branch VPA Transfer Function        -   3.4.2. CPCP 2-Branch VPA Transfer Function        -   3.4.3. Direct Cartesian 2-Branch VPA Transfer Function        -   3.4.4. Magnitude to Phase Shift Transform            -   3.4.4.1. Magnitude to Phase Shift Transform for                Sinusoidal Signals            -   3.4.4.2. Magnitude to Phase Shift Transform for Square                Wave Signals        -   3.4.5. Waveform Distortion Compensation    -   3.5. Output Stage        -   3.5.1. Output Stage Embodiments        -   3.5.2. Output Stage Current Shaping        -   3.5.3. Output Stage Protection    -   3.6. Harmonic Control    -   3.7. Power Control    -   3.8. Exemplary Vector Power Amplifier Embodiment

4. Additional Exemplary Embodiments and Implementations

-   -   4.1. Overview        -   4.1.1. Control of Output Power and Power Efficiency        -   4.1.2. Error Compensation and/or Correction        -   4.1.3. Multi-Band Multi-Mode Operation    -   4.2. Digital Control Module    -   4.3. VPA Analog Core        -   4.3.1. VPA Analog Core Implementation A        -   4.3.2. VPA Analog Core Implementation B        -   4.3.3. VPA Analog Core Implementation C    -   5. Real-Time Amplifier Class Control of VPA Output Stage    -   6. Additional MISO Design Concepts    -   7. Summary    -   8. Conclusion

1. INTRODUCTION

Methods, apparatuses and systems for vector combining poweramplification are disclosed herein.

Vector combining power amplification is an approach for optimizinglinearity and power efficiency simultaneously. Generally speaking, andreferring to flowchart 502 in FIG. 50, in step 504 a time-varyingcomplex envelope input signal, with varying amplitude and phase, isdecomposed into constant envelope constituent signals. In step 506, theconstant envelope constituent signals are amplified, and then in step508 summed to generate an amplified version of the input complexenvelope signal. Since substantially constant envelope signals may beamplified with minimal concern for non-linear distortion, the result ofsumming the constant envelope signals suffers minimal non-lineardistortion while providing optimum efficiency.

Accordingly, vector combining power amplification allows for non-linearpower amplifiers to be used to efficiently amplify complex signalswhilst maintaining minimal non-linear distortion levels.

For purposes of convenience, and not limitation, methods and systems ofthe present invention are sometimes referred to herein as vector poweramplification (VPA) methods and systems.

A high-level description of VPA methods and systems according toembodiments of the present invention is now provided. For the purpose ofclarity, certain terms are first defined below. The definitionsdescribed in this section are provided for convenience purposes only,and are not limiting. The meaning of these terms will be apparent topersons skilled in the art(s) based on the entirety of the teachingsprovided herein. These terms may be discussed throughout thespecification with additional detail.

The term signal envelope, when used herein, refers to an amplitudeboundary within which a signal is contained as it fluctuates in the timedomain. Quadrature-modulated signals can be described byr(t)=i(t)·cos(ωc·t)+q(t)·sin(ωc·t) where i(t) and q(t) representin-phase and quadrature signals with the signal envelope e(t), beingequal to e(t)=√{square root over (i(t)²+q(t)²)}{square root over(i(t)²+q(t)²)} and the phase angle associated with r(t) is related toarctan (q(t)/i(t).

The term constant envelope signal, when used herein, refers to in-phaseand quadrature signals where e(t)=√{square root over(i(t)²+q(t)²)}{square root over (i(t)²+q(t)²)}, with e(t) having arelatively or substantially constant value.

The term time-varying envelope signal, when used herein, refers to asignal having a time-varying signal envelope. A time-varying envelopesignal can be described in terms of in-phase and quadrature signals ase(t)=√{square root over (i(t)²+q(t)²)}{square root over (i(t)²+q(t)²)},with e(t) having a time-varying value.

The term phase shifting, when used herein, refers to delaying oradvancing the phase component of a time-varying or constant envelopesignal relative to a reference phase.

1.1) Example Generation of Complex Envelope Time-Varying Input Signals

FIGS. 1A and 1B are examples that illustrate the generation oftime-varying envelope and phase complex input signals. In FIG. 1A,time-varying envelope carrier signals 104 and 106 are input into phasecontroller 110. Phase controller 110 manipulates the phase components ofsignals 104 and 106. In other words, phase controller 110 may phaseshift signals 104 and 106. Resulting signals 108 and 112, accordingly,may be phased shifted relative to signals 104 and 106. In the example ofFIG. 1A, phase controller 110 causes a phase reversal (180 degree phaseshift) in signals 104 and 106 at time instant t₀, as can be seen fromsignals 108 and 112. Signals 108 and 112 represent time-varying complexcarrier signals. Signals 108 and 112 have both time-varying envelopesand phase components. When summed, signals 108 and 112 result in signal114. Signal 114 also represents a time-varying complex signal. Signal114 may be an example input signal into VPA embodiments of the presentinvention (for example, an example input into step 504 of FIG. 50).

Time-varying complex signals may also be generated as illustrated inFIG. 1B. In FIG. 1B, signals 116 and 118 represent baseband signals. Forexample, signals 116 and 118 may be in-phase (I) and quadrature (Q)baseband components of a signal. In the example of FIG. 1B, signals 116and 118 undergo a zero crossing as they transition from +1 to −1.Signals 116 and 118 are multiplied by signal 120 or signal 120 phaseshifted by 90 degrees. Signal 116 is multiplied by a 0 degree shiftedversion of signal 120. Signal 118 is multiplied by a 90 degree shiftedversion of signal 120. Resulting signals 122 and 124 representtime-varying complex carrier signals. Note that signals 122 and 124 haveenvelopes that vary according to the time-varying amplitudes of signals116 and 118. Further, signals 122 and 124 both undergo phase reversalsat the zero crossings of signals 116 and 118. Signals 122 and 124 aresummed to result in signal 126. Signal 126 represents a time-varyingcomplex signal. Signal 126 may represent an example input signal intoVPA embodiments of the present invention. Additionally, signals 116 and118 may represent example input signals into VPA embodiments of thepresent invention.

1.2) Example Generation of Time-Varying Complex Envelope Signals fromConstant Envelope Signals

The description in this section generally relates to the operation ofstep 508 in FIG. 50. FIG. 1C illustrates three examples for thegeneration of time-varying complex signals from the sum of two or moresubstantially constant envelope signals. A person skilled in the artwill appreciate, however, based on the teachings provided herein thatthe concepts illustrated in the examples of FIG. 1C can be similarlyextended to the case of more than two constant envelope signals.

In example 1 of FIG. 1C, constant envelope signals 132 and 134 are inputinto phase controller 130. Phase controller 130 manipulates phasecomponents of signals 132 and 134 to generate signals 136 and 138,respectively. Signals 136 and 138 represent substantially constantenvelope signals, and are summed to generate signal 140. The phasorrepresentation in FIG. 1C, associated with example 1 illustrates signals136 and 138 as phasors P₁₃₆ and P₁₃₈, respectively. Signal 140 isillustrated as phasor P₁₄₀. In example 1, P₁₃₆ and P₁₃₈ aresymmetrically phase shifted by an angle φ₁ relative to a referencesignal assumed to be aligned with the real axis of the phasorrepresentation. Correspondingly, time domain signals 136 and 138 arephase shifted in equal amounts but opposite directions relative to thereference signal. Accordingly, P₁₄₀, which is the sum of P₁₃₆ and P₁₃₈,is in-phase with the reference signal.

In example 2 of FIG. 1C, substantially constant envelope signals 132 and134 are input into phase controller 130. Phase controller 130manipulates phase components of signals 132 and 134 to generate signals142 and 144, respectively. Signals 142 and 144 are substantiallyconstant envelope signals, and are summed to generate signal 150. Thephasor representation associated with example 2 illustrates signals 142and 144 as phasors P₁₄₂ and P₁₄₄, respectively. Signal 150 isillustrated as phasor P₁₅₀. In example 2, P₁₄₂ and P₁₄₄ aresymmetrically phase shifted relative to a reference signal. Accordingly,similar to P₁₄₀, P₁₅₀ is also in-phase with the reference signal. P₁₄₂and P₁₄₄, however, are phase shifted by an angle whereby φ₂≠φ₁ relativeto the reference signal. P₁₅₀, as a result, has a different magnitudethan P₁₄₀ of example 1. In the time domain representation, it is notedthat signals 140 and 150 are in-phase but have different amplitudesrelative to each other.

In example 3 of FIG. 1C, substantially constant envelope signals 132 and134 are input into phase controller 130. Phase controller 130manipulates phase components of signals 132 and 134 to generate signals146 and 148, respectively. Signals 146 and 148 are substantiallyconstant envelope signals, and are summed to generate signal 160. Thephasor representation associated with example 3 illustrates signals 146and 148 as phasors P₁₄₆ and P₁₄₈, respectively. Signal 160 isillustrated as phasor P₁₆₀. In example 3, P₁₄₆ is phased shifted by anangle φ₃ relative to the reference signal. P₁₄₈ is phase shifted by anangle φ₄ relative to the reference signal. φ₃ and φ₄ may or may not beequal. Accordingly, P₁₆₀, which is the sum of P₁₄₆ and P₁₄₈, is nolonger in-phase with the reference signal. P₁₆₀ is phased shifted by anangle Θ relative to the reference signal. Similarly, P₁₆₀ is phaseshifted by Θ relative to P₁₄₀ and P₁₅₀ of examples 1 and 2. P₁₆₀ mayalso vary in amplitude relative to P₁₄₀ as illustrated in example 3.

In summary, the examples of FIG. 1C demonstrate that a time-varyingamplitude signal can be obtained by the sum of two or more substantiallyconstant envelope signals (Example 1). Further, the time-varying signalcan have amplitude changes but no phase changes imparted thereon byequally shifting in opposite directions the two or more substantiallyconstant envelope signals (Example 2). Equally shifting in the samedirection the two or more constant envelope constituents of the signal,phase changes but no amplitude changes can be imparted on thetime-varying signal. Any time-varying amplitude and phase signal can begenerated using two or more substantially constant envelope signals(Example 3).

It is noted that signals in the examples of FIG. 1C are shown assinusoidal waveforms for purpose of illustration only. A person skilledin the art will appreciate based on the teachings herein that othertypes of waveforms may also have been used. It should also be noted thatthe examples of FIG. 1C are provided herein for the purpose ofillustration only, and may or may not correspond to a particularembodiment of the present invention.

1.3) Vector Power Amplification Overview

A high-level overview of vector power amplification is now provided.FIG. 1D illustrates the power amplification of an exemplary time-varyingcomplex input signal 172. Signals 114 and 126 as illustrated in FIGS. 1Aand 1B may be examples of signal 172. Further, signal 172 may begenerated by or comprised of two or more constituent signals such as 104and 106 (FIG. 1A), 108 and 112 (FIG. 1A), 116 and 118 (FIG. 1B), and 122and 124 (FIG. 1B).

In the example of FIG. 1D, VPA 170 represents a VPA system embodimentaccording to the present invention. VPA 170 amplifies signal 172 togenerate amplified output signal 178. Output signal 178 is amplifiedefficiently with minimal distortion.

In the example of FIG. 1D, signals 172 and 178 represent voltage signalsV_(in)(t) and V_(olt)(t), respectively. At any time instant, in theexample of FIG. 1D, V_(in)(t) and V_(olt)(t) are related such thatV_(olt)(t)=Kev_(in)(tat′), where K is a scale factor and t′ represents atime delay that may be present in the VPA system. For power implication,

${\frac{V_{out}^{2}(t)}{Z_{out}} > \frac{V_{in}^{2}(t)}{Z_{in}}},$

where output signal 178 is a power amplified version of input signal172.

Linear (or substantially linear) power amplification of time-varyingcomplex signals, as illustrated in FIG. 1D, is achieved according toembodiments of the present as shown in FIG. 1E.

FIG. 1E is an example block diagram that conceptually illustrates avector power amplification embodiment according to embodiments of thepresent invention. In FIG. 1E, input signal 172 represents atime-varying complex signal. For example, input signal 172 may begenerated as illustrated in FIGS. 1A and 1B. In embodiments, signal 172may be a digital or an analog signal. Further, signal 172 may be abaseband or a carrier-based signal.

Referring to FIG. 1E, according to embodiments of the present invention,input signal 172 or equivalents thereof are input into VPA 182. In theembodiment of FIG. 1E, VPA 182 includes a state machine 184 and analogcircuitry 186. State machine 184 may include digital and/or analogcomponents. Analog circuitry 186 includes analog components. VPA 182processes input signal 172 to generate two or more signals 188-{1, . . ., n}, as illustrated in FIG. 1E. As described with respect to signals136, 138, 142, 144, and 146, 148, in FIG. 1C, signals 188-{1, . . . , n}may or may not be phase shifted relative to each other over differentperiods of time. Further, VPA 182 generates signals 188-{1, . . . , n}such that a sum of signals 188-{1, . . . , n} results in signal 194which, in certain embodiments, can be an amplified version of signal172.

Still referring to FIG. 1E, signals 188-{1, . . . , n} are substantiallyconstant envelope signals. Accordingly, the description in the priorparagraph corresponds to step 504 in FIG. 50.

In the example of FIG. 1E, generally corresponding to step 506 in FIG.50, constant envelope signals 188-{1, . . . , n} are each independentlyamplified by a corresponding power amplifier (PA) 190-{1, . . . , n} togenerate amplified signals 192-{1, . . . , n}. In embodiments, PAs190-{1, . . . , n} amplify substantially equally respective constantenvelope signals 188-{1, . . . , n}. Amplified signals 192-{1, . . . ,n} are substantially constant envelope signals, and in step 508 aresummed to generate output signal 194. Note that output signal 194 can bea linearly (or substantially linearly) amplified version of input signal172. Output signal 194 may also be a frequency-upconverted version ofinput signal 172, as described herein.

2. GENERAL MATHEMATICAL OVERVIEW 2.1) Phasor Signal Representation

FIG. 1 illustrates a phasor representation {right arrow over (R)} 102 ofa signal r(t). A phasor representation of a signal is explicitlyrepresentative of the magnitude of the signal's envelope and of thesignal's phase shift relative to a reference signal. In this document,for purposes of convenience, and not limitation, the reference signal isdefined as being aligned with the real (Re) axis of the orthogonal spaceof the phasor representation. The invention is not, however, limited tothis embodiment. The frequency information of the signal is implicit inthe representation, and is given by the frequency of the referencesignal. For example, referring to FIG. 1, and assuming that the realaxis corresponds to a cos(ωt) reference signal, phasor {right arrow over(R)} would translate to the function r(t)=R(t) cos(ωt+φ(t)), where R isthe magnitude of {right arrow over (R)}.

Still referring to FIG. 1, it is noted that phasor {right arrow over(R)} can be decomposed into a real part phasor {right arrow over (I)}and an imaginary part phasor {right arrow over (Q)}. {right arrow over(I)} and {right arrow over (Q)} are said to be the in-phase andquadrature phasor components of {right arrow over (R)} with respect tothe reference signal. It is further noted that the signals thatcorrespond to {right arrow over (I)} and {right arrow over (Q)} arerelated to r(t) as I(t)=R(t)·cos(φ(t)) and Q(t)=R(t)·sin(φ(t)),respectively. In the time domain, signal r(t) can also be written interms of its in-phase and quadrature components as follows:

$\begin{matrix}\begin{matrix}{{r(t)} = {{{I(t)} \cdot {\cos ( {\omega \; t} )}} + {{Q(t)} \cdot {\sin ( {\omega \; t} )}}}} \\{= {{{R(t)} \cdot {\cos ( {\varphi (t)} )} \cdot {\cos ( {\omega \; t} )}} + {{R(t)} \cdot {\sin ( {\varphi (t)} )} \cdot {\sin ( {\omega \; t} )}}}}\end{matrix} & (1)\end{matrix}$

Note that, in the example of FIG. 1, R(t) is illustrated at a particularinstant of time.

2.2) Time-Varying Complex Envelope Signals

FIG. 2 illustrates a phasor representation of a signal r(t) at twodifferent instants of time t1 and t2. It is noted that the magnitude ofthe phasor, which represents the magnitude of the signal's envelope, aswell as its relative phase shift both vary from time t1 to time t2. InFIG. 2, this is illustrated by the varying magnitude of phasors {rightarrow over (R₁)} and {right arrow over (R₂)} and their correspondingphase shift angles φ₁ and φ₂. Signal r(t), accordingly, is atime-varying complex envelope signal.

It is further noted, from FIG. 2, that the real and imaginary phasorcomponents of signal r(t) are also time-varying in amplitude.Accordingly, their corresponding time domain signals also havetime-varying envelopes.

FIGS. 3A-3C illustrate an example modulation to generate a time-varyingcomplex envelope signal. FIG. 3A illustrates a view of a signal m(t).FIG. 3B illustrates a view of a portion of a carrier signal c(t). FIG.3C illustrates a signal r(t) that results from the multiplication ofsignals m(t) and c(t).

In the example of FIG. 3A, signal m(t) is a time-varying magnitudesignal. m(t) further undergoes a zero crossing. Carrier signal c(t), inthe example of FIG. 3B, oscillates at some carrier frequency, typicallyhigher than that of signal m(t).

From FIG. 3C, it can be noted that the resulting signal r(t) has atime-varying envelope. Further, it is noted, from FIG. 3C, that r(t)undergoes a reversal in phase at the moment when the modulating signalm(t) crosses zero. Having both non-constant envelope and phase, r(t) issaid to be a time-varying complex envelope signal.

2.3 Constant Envelope Decomposition of Time-Varying Envelope Signals

Any phasor of time-varying magnitude and phase can be obtained by thesum of two or more constant magnitude phasors having appropriatelyspecified phase shifts relative to a reference phasor.

FIG. 3D illustrates a view of an example time-varying envelope and phasesignal S(t). For ease of illustration, signal S(t) is assumed to be asinusoidal signal having a maximum envelope magnitude A. FIG. 3D furthershows an example of how signal S(t) can be obtained, at any instant oftime, by the sum of two constant envelope signals S₁(t) and S₂(t).Generally, S₁(t)=A₁ sin(ωt+φ₁(t)) and S₁(t)=A₂ sin(ωt+φ₂(t)).

For the purpose of illustration, three views are provided in FIG. 3Dthat illustrate how by appropriately phasing signals S₁(t) and S₂(t)relative to S(t), signals S₁(t) and S₂(t) can be summed so thatS(t)=K(S₁(t)+S₂(t)) where K is a constant. In other words, signal S(t)can be decomposed, at any time instant, into two or more signals. FromFIG. 3D, over period T₁, S₁(t) and S₂(t) are both in-phase relative tosignal S(t), and thus sum to the maximum envelope magnitude A of signalS(t). Over period T₃, however, signals S₁(t) and S₂(t) are 180 degreeout-of-phase relative to each other, and thus sum to a minimum envelopemagnitude of signal S(t).

The example of FIG. 3D illustrates the case of sinusoidal signals. Aperson skilled in the art, however, will understand that anytime-varying envelope, which modulates a carrier signal that can berepresented by a Fourier series or Fourier transform, can be similarlydecomposed into two or more substantially constant envelope signals.Thus, by controlling the phase of a plurality of substantially constantenvelope signals, any time-varying complex envelope signal can begenerated.

3. VECTOR POWER AMPLIFICATION METHODS AND SYSTEMS

Vector power amplification methods and systems according to embodimentsof the present invention rely on the ability to decompose anytime-varying envelope signal into two or more substantially constantenvelope constituent signals or to receive or generate such constituentsignals, amplify the constituent signals, and then sum the amplifiedsignals to generate an amplified version of the time-varying complexenvelope signal.

In sections 3.1-3.3, vector power amplification (VPA) embodiments of thepresent invention are provided, including 4-branch and 2-branchembodiments. In the description, each VPA embodiment is first presentedconceptually using a mathematical derivation of underlying concepts ofthe embodiment. An embodiment of a method of operation of the VPAembodiment is then presented, followed by various system levelembodiments of the VPA embodiment.

Section 3.4 presents various embodiments of control modules according toembodiments of the present invention. Control modules according toembodiments of the present invention may be used to enable certain VPAembodiments of the present invention. In some embodiments, the controlmodules are intermediary between an input stage of the VPA embodimentand a subsequent vector modulation stage of the VPA embodiment.

Section 3.5 describes VPA output stage embodiments according toembodiments of the present invention. Output stage embodiments aredirected to generating the output signal of a VPA embodiment.

Section 3.6 is directed to harmonic control according to embodiments ofthe present invention. Harmonic control may be implemented in certainembodiments of the present invention to manipulate the real andimaginary power in the harmonics of the VPA embodiment, thus increasingthe power present in the fundamental frequency at the output.

Section 3.7 is directed to power control according to embodiments of thepresent invention. Power control may be implemented in certainembodiments of the present invention in order to satisfy power levelrequirements of applications where VPA embodiments of the presentinvention may be employed.

3.1) Cartesian 4-Branch Vector Power Amplifier

According to one embodiment of the invention, herein called theCartesian 4-Branch VPA embodiment for ease of illustration and notlimitation, a time-varying complex envelope signal is decomposed into 4substantially constant envelope constituent signals. The constituentsignals are equally or substantially equally amplified individually, andthen summed to construct an amplified version of the originaltime-varying complex envelope signal.

It is noted that 4 branches are employed in this embodiment for purposesof illustration, and not limitation. The scope of the invention coversuse of other numbers of branches, and implementation of such variationswill be apparent to persons skilled in the art based on the teachingscontained herein.

In one embodiment, a time-varying complex envelope signal is firstdecomposed into its in-phase and quadrature vector components. In phasorrepresentation, the in-phase and quadrature vector components correspondto the signal's real part and imaginary part phasors, respectively.

As described above, magnitudes of the in-phase and quadrature vectorcomponents of a signal vary proportionally to the signal's magnitude,and are thus not constant envelope when the signal is a time-varyingenvelope signal. Accordingly, the 4-Branch VPA embodiment furtherdecomposes each of the in-phase and quadrature vector components of thesignal into four substantially constant envelope components, two for thein-phase and two for the quadrature signal components. This concept isillustrated in FIG. 4 using a phasor signal representation.

In the example of FIG. 4, phasors {right arrow over (I₁)} and {rightarrow over (I₂)} correspond to the real part phasors of an exemplarytime-varying complex envelope signal at two instants of time t1 and t2,respectively. It is noted that phasors {right arrow over (I₁)} and{right arrow over (I₂)} have different magnitudes.

Still referring to FIG. 4, at instant t1, phasor {right arrow over (I₁)}can be obtained by the sum of upper and lower phasors {right arrow over(I_(U) ₁ )} and {right arrow over (I_(L) ₁ )}. Similarly, at instant t2,phasor {right arrow over (I₂)} can be obtained by the sum of upper andlower phasors {right arrow over (I_(U) ₂ )} and {right arrow over (I_(L)₂ )}. Note that phasors {right arrow over (I_(U) ₁ )} and {right arrowover (I_(U) ₂ )} have equal or substantially equal magnitude. Similarly,phasors {right arrow over (I_(L) ₁ )} and {right arrow over (I_(L) ₂ )}have substantially equal magnitude. Accordingly, the real part phasor ofthe time-varying envelope signal can be obtained at any time instant bythe sum of at least two substantially constant envelope components.

The phase shifts of phasors {right arrow over (I_(U) ₁ )} and {rightarrow over (I_(L) ₁ )} relative to {right arrow over (I₁)}, as well asthe phase shifts of phasors {right arrow over (I_(U) ₂ )} and {rightarrow over (I_(L) ₂ )} relative to {right arrow over (I₂)} are setaccording to the desired magnitude of phasors {right arrow over (I₁)}and {right arrow over (I₂)}, respectively. In one case, when the upperand lower phasors are selected to have equal magnitude, the upper andlower phasors are symmetrically shifted in phase relative to the phasor.This is illustrated in the example of FIG. 4, and corresponds to {rightarrow over (I_(U) ₁ )}, {right arrow over (I_(L) ₁ )}, {right arrow over(I_(U) ₂ )}, and {right arrow over (I_(L) ₂ )} all having equalmagnitude. In a second case, the phase shift of the upper and lowerphasors are substantially symmetrically shifted in phase relative to thephasor. Based on the description herein, anyone skilled in the art willunderstand that the magnitude and phase shift of the upper and lowerphasors do not have to be exactly equal in value

As an example, it can be further verified that, for the case illustratedin FIG. 4, the relative phase shifts, illustrated as

$\frac{\varphi_{1}}{2}\mspace{14mu} {and}\mspace{14mu} \frac{\varphi_{2}}{2}$

in FIG. 4, are related to the magnitudes of normalized phasors {rightarrow over (I₁)} and {right arrow over (I₂)} as follows:

$\begin{matrix}{{{\frac{\varphi_{1}}{2} = {\cot^{- 1}( \frac{I_{1}}{2\sqrt{1 - \frac{I_{1}^{2}}{4}}} )}};}{and}} & (2) \\{{\frac{\varphi_{2}}{2} = {\cot^{- 1}( \frac{I_{2}}{2\sqrt{1 - \frac{I_{2}^{2}}{4}}} )}},} & (3)\end{matrix}$

wherein I₁ and I₂ represent the normalized magnitudes of phasors {rightarrow over (I₁)} and {right arrow over (I₂)}, respectively, and whereinthe domains of I₁ and I₂ are restricted appropriately according to thedomain over which equation (2) and (3) are valid. It is noted thatequations (2) and (3) are one representation for relating the relativephase shifts to the normalized magnitudes. Other, solutions, equivalentrepresentations, and/or simplified representations of equations (2) and(3) may also be employed. Look up tables relating relative phase shiftsto normalized magnitudes may also be used.

The concept describe above can be similarly applied to the imaginaryphasor or the quadrature component part of a signal r(t) as illustratedin FIG. 4. Accordingly, at any time instant t, imaginary phasor part{right arrow over (Q)} of signal r(t) can be obtained by summing upperand lower phasor components {right arrow over (Q_(U))} and {right arrowover (Q_(L))} of substantially equal and constant magnitude. In thisexample, {right arrow over (Q_(U))} and {right arrow over (Q_(L))} aresymmetrically shifted in phase relative to {right arrow over (Q)} by anangle set according to the magnitude of {right arrow over (Q)} at timet. The relationship of {right arrow over (Q_(U))} and {right arrow over(Q_(L))} to the desired phasor {right arrow over (Q)} are related asdefined in equations 2 and 3 by substituting Q₁ and Q₂ for I₁ and I₂respectively.

It follows from the above discussion that, in phasor representation, anyphasor {right arrow over (R)} of variable magnitude and phase can beconstructed by the sum of four substantially constant magnitude phasorcomponents:

{right arrow over (R)}={right arrow over (I _(U))}+{right arrow over (I_(L))}+{right arrow over (Q _(U))}+{right arrow over (Q _(L))};

{right arrow over (I _(U))}+{right arrow over (I _(L))}={right arrowover (I)};

{right arrow over (Q _(U))}+{right arrow over (Q _(L))}={right arrowover (Q)};

I _(U) =I _(L)=constant;

Q _(U) =Q _(L)=constant;  (4)

where I_(U), I_(L), Q_(U), and Q_(L) represent the magnitudes of phasors{right arrow over (I_(U))}, {right arrow over (I_(L))}, {right arrowover (Q_(U))}, and {right arrow over (Q_(L))}, respectively.

Correspondingly, in the time domain, a time-varying complex envelopesinusoidal signal r(t)=R(t) cos(ωt+φ) is constructed by the sum of fourconstant envelope signals as follows:

$\begin{matrix}{\mspace{79mu} {{{{r(t)} = {{I_{U}(t)} + {I_{L}(t)} + {Q_{U}(t)} + {Q_{L}(t)}}};}{{{I_{U}(t)} = {{{{sgn}( \overset{->}{I} )} \times I_{U} \times {\cos ( \frac{\varphi_{I}}{2} )} \times {\cos ( {\omega \; t} )}} + {I_{U} \times {\sin ( \frac{\varphi_{I}}{2} )} \times {\sin ( {\omega \; t} )}}}};}{{{I_{L}(t)} = {{{{sgn}( \overset{->}{I} )} \times I_{L} \times {\cos ( \frac{\varphi_{I}}{2} )} \times {\cos ( {\omega \; t} )}} - {I_{L} \times {\sin ( \frac{\varphi_{I}}{2} )} \times {\sin ( {\omega \; t} )}}}};}{{{Q_{U}(t)} = {{{- {{sgn}( \overset{->}{Q} )}} \times Q_{U} \times {\cos ( \frac{\varphi_{Q}}{2} )} \times {\sin ( {\omega \; t} )}} + {Q_{U} \times {\sin ( \frac{\varphi_{Q}}{2} )} \times {\cos ( {\omega \; t} )}}}};}{{Q_{L}(t)} = {{{- {{sgn}( \overset{->}{Q} )}} \times Q_{L} \times {\cos ( \frac{\varphi_{Q}}{2} )} \times {\sin ( {\omega \; t} )}} - {Q_{L} \times {\sin ( \frac{\varphi_{Q}}{2} )} \times {{\cos ( {\omega \; t} )}.}}}}}} & (5)\end{matrix}$

where sgn({right arrow over (I)})=±1 depending on whether {right arrowover (I)} is in-phase or 180° degrees out-of-phase with the positivereal axis. Similarly, sgn({right arrow over (Q)})=±1 depending onwhether {right arrow over (Q)} is in-phase or 180° degrees out-of-phasewith the imaginary axis.

$\frac{\varphi_{I}}{2}$

corresponds to the phase shift of {right arrow over (I_(U))} and {rightarrow over (I_(L))} relative to the real axis. Similarly,

$\frac{\varphi_{Q}}{2}$

corresponds to the phase shift of {right arrow over (Q_(U))} and {rightarrow over (Q_(L))} relative to the imaginary axis.

$\frac{\varphi_{I}}{2}\mspace{14mu} {and}\mspace{14mu} \frac{\varphi_{Q}}{2}$

can be calculated using the equations given in (2) and (3).

Equations (5) can be further simplified as:

$\begin{matrix}{{{{r(t)} = {{I_{U}(t)} + {I_{L}(t)} + {Q_{U}(t)} + {Q_{L}(t)}}};}{{{I_{U}(t)} = {{{{sgn}( \overset{->}{I} )} \times I_{UX} \times {\cos ( {\omega \; t} )}} + {I_{UY} \times {\sin ( {\omega \; t} )}}}};}{{{I_{L}(t)} = {{{{sgn}( \overset{->}{I} )} \times I_{UX} \times {\cos ( {\omega \; t} )}} - {I_{UY} \times {\sin ( {\omega \; t} )}}}};}{where}{{{Q_{U}(t)} = {{{- Q_{UX}} \times {\cos ( {\omega \; t} )}} + {{{sgn}( \overset{->}{Q} )} \times Q_{UY} \times {\sin ( {\omega \; t} )}}}};}{{{Q_{L}(t)} = {{{Q_{UY} \times {\cos ( {\omega \; t} )}} - {{{sgn}( \overset{->}{Q} )} \times Q_{UY} \times {{\sin ( {\omega \; t} )}.I_{UX}}}} = {{I_{U} \times {\cos ( \frac{\varphi_{I}}{2} )}} = {I_{L} \times {\cos ( \frac{\varphi_{I}}{2} )}}}}},{I_{UY} = {{I_{U} \times {\sin ( \frac{\varphi_{I}}{2} )}} = {I_{L} \times {\sin ( \frac{\varphi_{I}}{2} )}}}},{Q_{UX} = {{Q_{U} \times {\sin ( \frac{\varphi_{Q}}{2} )}} = {Q_{L} \times {\sin ( \frac{\varphi_{Q}}{2} )}}}},{and}}{Q_{UY} = {{Q_{U} \times {\cos ( \frac{\varphi_{Q}}{2} )}} = {Q_{L} \times {{\cos ( \frac{\varphi_{Q}}{2} )}.}}}}} & (6)\end{matrix}$

It can be understood by a person skilled in the art that, whereas thetime domain representations in equations (5) and (6) have been providedfor the case of a sinusoidal waveform, equivalent representations can bedeveloped for non-sinusoidal waveforms using appropriate basisfunctions. Further, as understood by a person skilled in the art basedon the teachings herein, the above-describe two-dimensionaldecomposition into substantially constant envelope signals can beextended appropriately into a multi-dimensional decomposition.

FIG. 5 is an example block diagram of the Cartesian 4-Branch VPAembodiment. An output signal r(t) 578 of desired power level andfrequency characteristics is generated from baseband in-phase andquadrature components according to the Cartesian 4-Branch VPAembodiment.

In the example of FIG. 5, a frequency generator such as a synthesizer510 generates a reference signal A*cos(ωt) 511 having the same frequencyas that of output signal r(t) 578. It can be understood by a personskilled in the art that the choice of the reference signal is madeaccording to the desired output signal. For example, if the desiredfrequency of the desired output signal is 2.4 GHz, then the frequency ofthe reference signal is set to be 2.4 GHz. In this manner, embodimentsof the invention achieve frequency up-conversion.

Referring to FIG. 5, one or more phase splitters are used to generatesignals 521, 531, 541, and 551 based on the reference signal 511. In theexample of FIG. 5, this is done using phase splitters 512, 514, and 516and by applying 0° phase shifts at each of the phase splitters. A personskilled in the art will appreciate, however, that various techniques maybe used for generating signals 521, 531, 541, and 551 of the referencesignal 511. For example, a 1:4 phase splitter may be used to generatethe four replicas 521, 531, 541, and 551 in a single step or in theexample embodiment of FIG. 5, signal 511 can be directly coupled tosignals 521, 531, 541, 551 Depending on the embodiment, a variety ofphase shifts may also be applied to result in the desired signals 521,531, 541, and 551.

Still referring to FIG. 5, the signals 521, 531, 541, and 551 are eachprovided to a corresponding vector modulator 520, 530, 540, and 550,respectively. Vector modulators 520, 530, 540, and 550, in conjunctionwith their appropriate input signals, generate four constant envelopeconstituents of signal r(t) according to the equations provided in (6).In the example embodiment of FIG. 5, vector modulators 520 and 530generate the I_(U)(t) and I_(L)(t) components, respectively, of signalr(t). Similarly, vector modulators 540 and 550 generate the Q_(U)(t) andQ_(L)(t) components, respectively, of signal r(t).

The actual implementation of each of vector modulators 520, 530, 540,and 550 may vary. It will be understood by a person skilled in the art,for example, that various techniques exist for generating the constantenvelope constituents according to the equations in (6).

In the example embodiment of FIG. 5, each of vector modulators 520, 530,540, 550 includes an input phase splitter 522, 532, 542, 552 for phasingthe signals 522, 531, 541, 551. Accordingly, input phase splitters 522,532, 542, 552 are used to generate an in-phase and a quadraturecomponents or their respective input signals.

In each vector modulator 520, 530, 540, 550, the in-phase and quadraturecomponents are multiplied with amplitude information. In FIG. 5, forexample, multiplier 524 multiplies the quadrature component of signal521 with the quadrature amplitude information I_(UY) of I_(U)(t). Inparallel, multiplier 526 multiplies the in-phase replica signal with thein-phase amplitude information sgn(I)×I_(UX) of I_(U)(t).

To generate the I_(U)(t) constant envelope constituent signals 525 and527 are summed using phase splitter 528 or alternate summing techniques.The resulting signal 529 corresponds to the IU(t) component of signalr(t).

In similar fashion as described above, vector modulators 530, 540, and550, respectively, generate the I_(L)(t), Q_(U)(t), and Q_(L)(t)components of signal r(t). I_(L)(t), Q_(U)(t), and Q_(L)(t),respectively, correspond to signals 539, 549, and 559 in FIG. 5.

Further, as described above, signals 529, 539, 549, and 559 arecharacterized by having substantially equal and constant magnitudeenvelopes. Accordingly, when signals 529, 539, 549, and 559 are inputinto corresponding power amplifiers (PA) 562, 564, 566, and 568,corresponding amplified signals 563, 565, 567, and 569 are substantiallyconstant envelope signals.

Power amplifiers 562, 564, 566, and 568 amplify each of the signals 529,539, 549, 559, respectively. In an embodiment, substantially equal poweramplification is applied to each of the signals 529, 539, 549, and 559.In an embodiment, the power amplification level of PAs 562, 564, 566,and 568 is set according to the desired power level of output signalr(t).

Still referring to FIG. 5, amplified signals 563 and 565 are summedusing summer 572 to generate an amplified version 573 of the in-phasecomponent {right arrow over (I)}(t) of signal r(t). Similarly, amplifiedsignals 567 and 569 are summed using summer 574 to generate an amplifiedversion 575 of the quadrature component {right arrow over (Q)}(t) ofsignal r(t).

Signals 573 and 575 are summed using summer 576, as shown in FIG. 5,with the resulting signal corresponding to desired output signal r(t).

It must be noted that, in the example of FIG. 5, summers 572, 574, and576 are being used for the purpose of illustration only. Varioustechniques may be used to sum amplified signals 563, 565, 567, and 569.For example, amplified signals 563, 565, 567, and 569 may be summed allin one step to result in signal 578. In fact, according to various VPAembodiments of the present invention, it suffices that the summing isdone after amplification. Certain VPA embodiments of the presentinvention, as will be further described below, use minimally lossysumming techniques such as direct coupling via wire. Alternatively,certain VPA embodiments use conventional power combining techniques. Inother embodiments, as will be further described below, power amplifiers562, 564, 566, and 568 can be implemented as a multiple-inputsingle-output power amplifier.

Operation of the Cartesian 4-Branch VPA embodiment shall now be furtherdescribed with reference to the process flowchart of FIG. 6. The processbegins at step 610, which includes receiving the baseband representationof the desired output signal. In an embodiment, this involves receivingin-phase (I) and quadrature (Q) components of the desired output signal.In another embodiment, this involves receiving magnitude and phase ofthe desired output signal. In an embodiment of the Cartesian 4-BranchVPA embodiment, the I and Q are baseband components. In anotherembodiment, the I and Q are RF components and are down-converted tobaseband.

Step 620 includes receiving a clock signal set according to a desiredoutput signal frequency of the desired output signal. In the example ofFIG. 5, step 620 is achieved by receiving reference signal 511.

Step 630 includes processing the I component to generate first andsecond signals having the output signal frequency. The first and secondsignals have substantially constant and equal magnitude envelopes and asum equal to the I component. The first and second signals correspond tothe I_(U)(t) and I_(L)(t) constant envelope constituents describedabove. In the example of FIG. 5, step 630 is achieved by vectormodulators 520 and 530, in conjunction with their appropriate inputsignals.

Step 640 includes processing the Q component to generate third andfourth signals having the output signal frequency. The third and fourthsignals have substantially constant and equal magnitude envelopes and asum equal to the Q component. The third and fourth signals correspond tothe Q_(U)(t) and Q_(L)(t) constant envelope constituents describedabove. In the example of FIG. 5, step 630 is achieved by vectormodulators 540 and 550, in conjunction with their appropriate inputsignals.

Step 650 includes individually amplifying each of the first, second,third, and fourth signals, and summing the amplified signals to generatethe desired output signal. In an embodiment, the amplification of thefirst, second, third, and fourth signals is substantially equal andaccording to a desired power level of the desired output signal. In theexample of FIG. 5, step 650 is achieved by power amplifiers 562, 564,566, and 568 amplifying respective signals 529, 539, 549, and 559, andby summers 572, 574, and 576 summing amplified signals 563, 565, 567,and 569 to generate output signal 578.

FIG. 7A is a block diagram that illustrates an exemplary embodiment of avector power amplifier 700 implementing the process flowchart 600 ofFIG. 6. In the example of FIG. 7A, optional components are illustratedwith dashed lines. In other embodiments, additional components may beoptional.

Vector power amplifier 700 includes an in-phase (I) branch 703 and aquadrature (Q) branch 705. Each of the I and Q branches furthercomprises a first branch and a second branch.

In-phase (I) information signal 702 is received by an I Data TransferFunction module 710. In an embodiment, I information signal 702 includesa digital baseband signal. In an embodiment, I Data Transfer Functionmodule 710 samples I information signal 702 according to a sample clock706. In another embodiment, I information signal 702 includes an analogbaseband signal, which is converted to digital using ananalog-to-digital converter (ADC) (not shown in FIG. 7A) before beinginput into I Data Transfer Function module 710. In another embodiment, Iinformation signal 702 includes an analog baseband signal which input inanalog form into I Data Transfer Function module 710, which alsoincludes analog circuitry. In another embodiment, I information signal702 includes a RF signal which is down-converted to baseband beforebeing input into I Data Transfer Function module 710 using any of theabove described embodiments.

I Data Transfer Function module 710 processes I information signal 702,and determines in-phase and quadrature amplitude information of at leasttwo constant envelope constituent signals of I information signal 702.As described above with reference to FIG. 5, the in-phase and quadraturevector modulator input amplitude information corresponds tosgn(I)×I_(UX) and I_(UY), respectively. The operation of I Data TransferFunction module 710 is further described below in section 3.4.

I Data Transfer Function module 710 outputs information signals 722 and724 used to control the in-phase and quadrature amplitude components ofvector modulators 760 and 762. In an embodiment, signals 722 and 724 aredigital signals. Accordingly, each of signals 722 and 724 is fed into acorresponding digital-to-analog converter (DAC) 730 and 732,respectively. The resolution and sample rate of DACs 730 and 732 isselected to achieve the desired I component of the output signal 782.DACs 730 and 732 are controlled by DAC clock signals 723 and 725,respectively. DAC clock signals 723 and 725 may be derived from a sameclock signal or may be independent.

In another embodiment, signals 722 and 724 are analog signals, and DACs730 and 732 are not required.

In the exemplary embodiment of FIG. 7A, DACs 730 and 732 convert digitalinformation signals 722 and 724 into corresponding analog signals, andinput these analog signals into optional interpolation filters 731 and733, respectively. Interpolation filters 731 and 733, which also serveas anti-aliasing filters, shape the DACs outputs to produce the desiredoutput waveform. Interpolation filters 731 and 733 generate signals 740and 742, respectively. Signal 741 represents the inverse of signal 740.Signals 740-742 are input into vector modulators 760 and 762.

Vector modulators 760 and 762 multiply signals 740-742 withappropriately phased clock signals to generate constant envelopeconstituents of I information signal 702. The clock signals are derivedfrom a channel clock signal 708 having a rate according to a desiredoutput signal frequency. A plurality of phase splitters, such as 750 and752, for example, and phasors associated with the vector modulatormultipliers may be used to generate the appropriately phased clocksignals.

In the embodiment of FIG. 7A, for example, vector modulator 760modulates a 90° shifted channel clock signal with quadrature amplitudeinformation signal 740. In parallel, vector modulator 760 modulates anin-phase channel clock signal with in-phase amplitude information signal742. Vector modulator 760 combines the two modulated signals to generatea first modulated constant envelope constituent 761 of I informationsignal 702. Similarly, vector modulator 762 generates a second modulatedconstant envelope constituent 763 of I information signal 702, usingsignals 741 and 742. Signals 761 and 763 correspond, respectively, tothe I_(U)(t) and I_(L)(t) constant envelope components described withreference to FIG. 5.

In parallel and in similar fashion, the Q branch of vector poweramplifier 700 generates at least two constant envelope constituentsignals of quadrature (Q) information signal 704.

In the embodiment of FIG. 7A, for example, vector modulator 764generates a first constant envelope constituent 765 of Q informationsignal 704, using signals 744 and 746. Similarly, vector modulator 766generates a second constant envelope constituent 767 of Q informationsignal 704, using signals 745 and 746.

As described above with respect to FIG. 5, constituent signals 761, 763,765, and 767 have substantially equal and constant magnitude envelopes.In the exemplary embodiment of FIG. 7A, signals 761, 763, 765, and 767are, respectively, input into corresponding power amplifiers (PAs) 770,772, 774, and 776. PAs 770, 772, 774, and 776 can be linear ornon-linear power amplifiers. In an embodiment, PAs 770, 772, 774, and776 include switching power amplifiers.

Circuitry 714 and 716 (herein referred to as “autobias circuitry” forease of reference, and not limitation) and in this embodiment, controlthe bias of PAs 770, 772, 774, and 776 according to I and Q informationsignals 702 and 704. In the embodiment of FIG. 7A, autobias circuitry714 and 716 provide, respectively, bias signals 715 and 717 to PAs 770,772 and PAs 774, 776. Autobias circuitry 714 and 716 are furtherdescribed below in section 3.5. Embodiments of PAs 770, 772, 774, and776 are also discussed below in section 3.5.

In an embodiment, PAs 770, 772, 774, and 776 apply substantially equalpower amplification to respective substantially constant envelopesignals 761, 763, 765, and 767. In other embodiments, PA drivers areadditionally employed to provide additional power amplification. In theembodiment of FIG. 7A, PA drivers 794, 795, 796, and 797 are optionallyadded between respective vector modulators 760, 762, 764 766 andrespective PAs 770, 772, 774, and 776, in each branch of vector poweramplifier 700.

The outputs of PAs 770, 772, 774, and 776 are coupled together togenerate output signal 782 of vector power amplifier 700. In anembodiment, the outputs of PAs 770, 772, 774, and 776 are directlycoupled together using a wire. Direct coupling in this manner means thatthere is minimal or no resistive, inductive, or capacitive isolationbetween the outputs of PAs 770, 772, 774, and 776. In other words,outputs of PAs 770, 772, 774, and 776, are coupled together withoutintervening components. Alternatively, in an embodiment, the outputs ofPAs 770, 772, 774, and 776 are coupled together indirectly throughinductances and/or capacitances that result in low or minimal impedanceconnections, and/or connections that result in minimal isolation andminimal power loss. Alternatively, outputs of PAs 770, 772, 774, and 776are coupled using well known combining techniques, such as Wilkinson,hybrid, transformers, or known active combiners. In an embodiment, thePAs 770, 772, 774, and 776 provide integrated amplification and powercombining in a single operation. In an embodiment, one or more of thepower amplifiers and/or drivers described herein are implemented usingmultiple input, single output power amplification techniques, examplesof which are shown in FIGS. 7B, and 51A-H.

Output signal 782 includes the I and Q characteristics of I and Qinformation signals 702 and 704. Further, output signal 782 is of thesame frequency as that of its constituents, and thus is of the desiredup-converted output frequency. In embodiments of vector power amplifier700, a pull-up impedance 780 is coupled between the output of vectoramplifier 700 and a power supply. Output stage embodiments according topower amplification methods and systems of the present invention will befurther described below in section 3.5.

In other embodiments of vector power amplifier 700, process detectorsare employed to compensate for any process variations in circuitry ofthe amplifier. In the embodiment of FIG. 7A for example, processdetectors 791-793 are optionally added to monitor variations in PAdrivers 794-797 and phase splitter 750. In further embodiments,frequency compensation circuitry 799 may be employed to compensate forfrequency variations.

FIG. 7B is a block diagram that illustrates another exemplary embodimentof vector power amplifier 700. Optional components are illustrated withdashed lines, although other embodiments may have more or less optionalcomponents.

The embodiment illustrates a multiple-input single-output (MISO)implementation of the amplifier of FIG. 7A. In the embodiment of FIG.7B, constant envelope signals 761, 763, 765 and 767, output from vectormodulators 760, 762, 764, and 766, are input into MISO PAs 784 and 786.MISO PAs 784 and 786 are two-input single-output power amplifiers. In anembodiment, MISO PAs 784 and 786 include elements 770, 772, 774, 776,794-797 as shown in the embodiment of FIG. 7A or functional equivalencethereof. In another embodiment, MISO PAs 784 and 786 may include otherelements, such as optional pre-drivers and optional process detectioncircuitry. Further, MISO PAs 784 and 786 are not limited to beingtwo-input PAs as shown in FIG. 7B. In other embodiments as will bedescribed further below with reference to FIGS. 51A-H, PAs 784 and 786can have any number of inputs and outputs.

FIG. 8A is a block diagram that illustrates another exemplary embodiment800A of a vector power amplifier according to the Cartesian 4-Branch VPAmethod shown in FIG. 6. Optional components are illustrated with dashedlines, although other embodiments may have more or less optionalcomponents.

In the embodiment of FIG. 8A, a DAC 830 of sufficient resolution andsample rate replaces DACs 730, 732, 734, and 736 of the embodiment ofFIG. 7A. DAC 830's sample rate is controlled by a DAC clock signal 826.

DAC 830 receives in-phase and quadrature information signals 810 and 820from I Data Transfer Function module 710 and Q Data Transfer Functionmodule 712, respectively, as described above. In an embodiment, a inputselector 822 selects the order of signals 810 and 820 being input intoDAC 830.

DAC 830 may output a single analog signal at a time. In an embodiment, asample and hold architecture may be used to ensure proper signal timingto the four branches of the amplifier, as shown in FIG. 8A.

DAC 830 sequentially outputs analog signals 832, 834, 836, 838 to afirst set of sample-and-hold circuits 842, 844, 846, and 848. In anembodiment, DAC 830 is clocked at a sufficient rate to emulate theoperation of DACs 730, 732, 734, and 736 of the embodiment of FIG. 7A.An output selector 824 determines which of output signals 832, 834, 836,and 838 should be selected for output.

DAC 830's DAC clock signal 826, output selector signal 824, inputselector 822, and sample-and-hold clocks 840A-D, and 850 are controlledby a control module that can be independent or integrated into transferfunction modules 710 and/or 712.

In an embodiment, sample-and-hold circuits (S/H) 842, 844, 846, and 848sample and hold the received analog values from DAC 830 according to aclock signals 840A-D. Sample-and-hold circuits 852, 854, 856, and 858sample and hold the analog values from sample and hold circuits 842,844, 846, and 848 respectively. In turn, sample-and-hold circuits 852,854, 856, and 858 hold the received analog values, and simultaneouslyrelease the values to vector modulators 760, 762, 764, and 766 accordingto a common clock signal 850. In another embodiment, sample-and-holdcircuits 852, 854, 856, and 858 release the values to optionalinterpolation filters 731, 733, 735, and 737 which are alsoanti-aliasing filters. In an embodiment, a common clock signal 850 isused in order to ensure that the outputs of S/H 852, 854, 856, and 858are time-aligned.

Other aspects of vector power amplifier 800A substantially correspond tothose described above with respect to vector power amplifier 700.

FIG. 8B is a block diagram that illustrates another exemplary embodiment800B of a vector power amplifier according to the Cartesian 4-Branch VPAmethod shown in FIG. 6. Optional components are illustrated with dashedlines, although other embodiments may have more or less optionalcomponents.

Embodiment 800B illustrates another single DAC implementation of thevector power amplifier. However, in contrast to the embodiment of FIG.8A, the sample and hold architecture includes a single set ofsample-and-hold (S/H) circuits. As shown in FIG. 8B, S/H 842, 844, 846,and 848 receive analog values from DAC 830, illustrated as signals 832,834, 836, and 838. Each of S/H circuits 842, 844, 846 and 848 releaseits received value according to a different clock 840A-D as shown. Thetime difference between analog samples used for to generate signals 740,741, 742, 744, 745, and 746 can be compensated for in transfer functions710 and 712. According to the embodiment of FIG. 8B, one level of S/Hcircuitry can be eliminated relative to the embodiment of FIG. 8A,thereby reducing the size and the complexity of the amplifier.

Other aspects of vector power amplifier 800B substantially correspond tothose described above with respect to vector power amplifiers 700 and800A.

FIG. 8C is a block diagram that illustrates another exemplary embodiment800C of vector power amplifier 700. Optional components are illustratedwith dashed lines, although other embodiments may have more or lessoptional components. The embodiment of FIG. 8C illustrates amultiple-input single-output (MISO) implementation of the amplifier ofFIG. 8A. In the embodiment of FIG. 8C, constant envelope signals 761,763, 765 and 767, output from vector modulators 760, 762, 764, and 766,are input into MISO PAs 860 and 862. MISO PAs 860 and 862 are two-inputsingle-output power amplifiers. In an embodiment, MISO PAs 860 and 862include elements 770, 772, 774, 776, 794-797 as shown in the embodimentof FIG. 7A or functional equivalence thereof. In another embodiment,MISO PAs 860 and 862 may include other elements, such as optionalpre-drivers and optional process detection circuitry. In anotherembodiment, MISO PAs 860 and 862 may include other elements, such aspre-drivers, not shown in the embodiment of FIG. 7A. Further, MISO PAs860 and 862 are not limited to being two-input PAs as shown in FIG. 8C.In other embodiments as will be described further below with referenceto FIGS. 51A-H, PAs 860 and 862 can have any number of inputs andoutputs.

Other aspects of vector power amplifier 800C substantially correspond tothose described above with respect to vector power amplifiers 700 and800A.

FIG. 8D is a block diagram that illustrates another exemplary embodiment800D of vector power amplifier 700. Optional components are illustratedwith dashed lines, although other embodiments may have more or lessoptional components. The embodiment of FIG. 8D illustrates amultiple-input single-output (MISO) implementation of the amplifier ofFIG. 8B. In the embodiment of FIG. 8D, constant envelope signals 761,763, 765 and 767, output from vector modulators 760, 762, 764, and 766,are input into MISO PAs 870 and 872. MISO PAs 870 and 872 are two-inputsingle-output power amplifiers. In an embodiment, MISO PAs 870 and 872include elements 770, 772, 774, 776, 794-797 as shown in the embodimentof FIG. 7A or functional equivalence thereof. In another embodiment,MISO PAs 870 and 872 may include other elements, such as optionalpre-drivers and optional process detection circuitry. In anotherembodiment, MISO PAs 870 and 872 may include other elements, such aspre-drivers, not shown in the embodiment of FIG. 7A. Further, MISO PAs870 and 872 are not limited to being two-input PAs as shown in FIG. 8D.In other embodiments as will be described further below with referenceto FIGS. 51A-H, PAs 870 and 872 can have any number of inputs andoutputs.

Other aspects of vector power amplifier 800D substantially correspond tothose described above with respect to vector power amplifiers 700 and800B.

3.2) Cartesian-Polar-Cartesian-Polar 2-Branch Vector Power Amplifier

A Cartesian-Polar-Cartesian-Polar (CPCP) 2-Branch VPA embodiment shallnow be described (The name of this embodiment is provided for ease ofreference, and is not limiting).

According to the Cartesian-Polar-Cartesian-Polar (CPCP) 2-Branch VPAmethod, a time-varying complex envelope signal is decomposed into 2substantially constant envelope constituent signals. The constituentsignals are individually amplified, and then summed to construct anamplified version of the original time-varying complex envelope signal.In addition, the phase angle of the time-varying complex envelope signalis determined and the resulting summation of the constituent signals arephase shifted by the appropriate angle.

In one embodiment of the CPCP 2-Branch VPA method, a magnitude and aphase angle of a time-varying complex envelope signal are calculatedfrom in-phase and quadrature components of a signal. Given the magnitudeinformation, two substantially constant envelope constituents arecalculated from a normalized version of the desired time-varyingenvelope signal, wherein the normalization includes implementationspecific manipulation of phase and/or amplitude. The two substantiallyconstant envelope constituents are then phase shifted by an appropriateangle related to the phase shift of the desired time-varying envelopesignal. The substantially constant envelope constituents are thenindividually amplified substantially equally, and summed to generate anamplified version of the original desired time-varying envelope signal.

FIGS. 9A and 9B conceptually illustrate the CPCP 2-Branch VPA embodimentusing a phasor signal representation. In FIG. 9A, phasor {right arrowover (R_(in))} represents a time-varying complex envelope input signalr(t). At any instant of time, {right arrow over (R_(in))} reflects amagnitude and a phase shift angle of signal r(t). In the example shownin FIG. 9A, {right arrow over (R_(in))} is characterized by a magnitudeR and a phase shift angle θ. As described above, the phase shift angleis measured relative to a reference signal.

Referring to FIG. 9A, {right arrow over (R′)} represents the relativeamplitude component of kin generated by {right arrow over (U)}′ and{right arrow over (L)}′.

Still referring to FIG. 9A, it is noted that, at any time instant,{right arrow over (R′)} can be obtained by the sum of an upper phasor{right arrow over (U′)} and a lower phasor {right arrow over (L′)}.Further, {right arrow over (U′)} and {right arrow over (L′)} can bemaintained to have substantially constant magnitude. The phasors, {rightarrow over (U′)} and {right arrow over (L′)}, accordingly, represent twosubstantially constant envelope signals. r′(t) can thus be obtained, atany time instant, by the sum of two substantially constant envelopesignals that correspond to phasors {right arrow over (U′)} and {rightarrow over (L′)}.

The phase shifts of phasors {right arrow over (U′)} and {right arrowover (L′)} relative to {right arrow over (R′)} are set according to thedesired magnitude R of {right arrow over (R′)}. In the simplest case,when upper and lower phasors {right arrow over (U′)} and {right arrowover (L′)} are selected to have equal magnitude, upper and lower phasors{right arrow over (U′)} and {right arrow over (L′)} are substantiallysymmetrically shifted in phase relative to {right arrow over (R′)}. Thisis illustrated in the example of FIG. 9A. It is noted that terms andphrases indicating or suggesting orientation, such as but not limited to“upper and lower” are used herein for ease of reference and are notfunctionally or structurally limiting.

It can be verified that, for the case illustrated in FIG. 9A, the phaseshift of {right arrow over (U′)} and {right arrow over (L′)} relative to{right arrow over (R′)}, illustrated as angle

$\frac{\varphi}{2}$

in FIG. 9A, is related to the magnitude of {right arrow over (R′)} asfollows:

$\begin{matrix}{\frac{\varphi}{2} = {\cot^{- 1}( \frac{R}{2\sqrt{1 - \frac{R^{2}}{4}}} )}} & (7)\end{matrix}$

where R represents a normalized magnitude of phasor {right arrow over(R′)}.

Equation (7) can further be reduced to

$\begin{matrix}{\frac{\varphi}{2} = {\cos^{- 1}( \frac{R}{2} )}} & (7.10)\end{matrix}$

where R represents a normalized magnitude of phasor {right arrow over(R′)}.

Alternatively, any substantially equivalent mathematical equations orother substantially equivalent mathematical techniques such as look uptables can be used.

It follows from the above discussion that, in phasor representation, anyphasor {right arrow over (R′)} of variable magnitude and phase can beconstructed by the sum of two constant magnitude phasor components:

{right arrow over (R′)}={right arrow over (U′)}+{right arrow over (L′)}

|{right arrow over (U)}|=|{right arrow over (L)}=A=constant  (8)

Correspondingly, in the time domain, a time-varying envelope sinusoidalsignal r′(t)=R(t)×cos(ωt) is constructed by the sum of two constantenvelope signals as follows:

$\begin{matrix}{{{{r^{\prime}(t)} = {{U^{\prime}(t)} + {L^{\prime}(t)}}};}{{{U^{\prime}(t)} = {A \times {\cos ( {{\omega \; t} + \frac{\varphi}{2}} )}}};}{{{L^{\prime}(t)} = {A \times {\cos ( {{\omega \; t} - \frac{\varphi}{2}} )}}};}} & (9)\end{matrix}$

where A is a constant and

$\frac{\varphi}{2}$

is as shown in equation (7).

From FIG. 9A, it can be further verified that equations (9) can berewritten as:

r′(t)=U′(t)+L′(t);

U′(t)=C cos(ωt)+α sin(ωt);

L′(t)=C cos(ωt)−β sin(ωt);  (10)

where C denotes the real part component of phasors {right arrow over(U′)} and {right arrow over (L′)} and is equal to

$A \times {{\cos ( \frac{\varphi}{2} )}.}$

Note that C is a common component of {right arrow over (U′)} and {rightarrow over (L′)}. α and β denote the imaginary part components ofphasors {right arrow over (U′)} and {right arrow over (L′)},respectively.

${r^{\prime}(t)} = {{2C \times {\cos ( {\omega \; t} )}} = {2A \times {\cos ( \frac{\varphi}{2} )} \times {{\cos ( {\omega \; t} )}.}}}$

Accordingly, from equations (12),

$\alpha = {\beta = {A \times {{\sin ( \frac{\varphi}{2} )}.}}}$

As understood by a person skilled in the art based on the teachingsherein, other equivalent and/or simplified representations of the aboverepresentations of the quantities A, B, and C may also be used,including look up tables, for example.

Note that {right arrow over (R_(in))} is shifted by θ degrees relativeto {right arrow over (R′)}. Accordingly, using equations (8), it can bededuced that:

{right arrow over (R _(in))}={right arrow over (R′)}e ^(jθ)=({rightarrow over (U′)}+{right arrow over (L′)})e ^(jθ) ={right arrow over(U′)}e ^(jθ) +{right arrow over (L′)}e ^(jθ)  (11)

Equations (11) imply that a representation of {right arrow over (R_(in))} can be obtained by summing phasors {right arrow over (U′)} and {rightarrow over (L′)}, described above, shifted by θ degrees. Further, anamplified output version, {right arrow over (R_(out) )} of {right arrowover (R_(in) )} can be obtained by separately amplifying substantiallyequally each of the θ degrees shifted versions of phasors {right arrowover (U′)} and {right arrow over (L′)}, and summing them. FIG. 9Billustrates this concept. In FIG. 9B, phasors {right arrow over (U′)}and {right arrow over (L′)} represent θ degrees shifted and amplifiedversions of phasors {right arrow over (U′)} and {right arrow over (L′)}.Note that, since {right arrow over (U′)} and {right arrow over (L′)} areconstant magnitude phasors, {right arrow over (U)} and {right arrow over(L)} are also constant magnitude phasors. Phasors {right arrow over (U)}and {right arrow over (L)} sum, as shown FIG. 9B, to phasor {right arrowover (R_(out) )} which is a power amplified version of input signal{right arrow over (R_(in))}.

Equivalently, in the time domain, it can be shown that:

r _(out)(t)=U(t)+L(t);

U(t)=K[C cos(a+θ)+a sin(ωt+θ)];

L(t)=K[C cos(ωt+θ)−β sin(ωt+θ)].  (12)

where r_(out)(t) corresponds to the time domain signal represented byphasor {right arrow over (R_(out))}, U(t) and L(t) correspond to thetime domain signals represents by phasors {right arrow over (U)} and{right arrow over (L)}, and K is the power amplification factor.

A person skilled in the art will appreciate that, whereas the timedomain representations in equations (9) and (10) have been provided forthe case of a sinusoidal waveform, equivalent representations can bedeveloped for non-sinusoidal waveforms using appropriate basisfunctions.

FIG. 10 is a block diagram that conceptually illustrates an exemplaryembodiment 1000 of the CPCP 2-Branch VPA embodiment. An output signalr(t) of desired power level and frequency characteristics is generatedfrom in-phase and quadrature components according to the CPCP 2-BranchVPA embodiment.

In the example of FIG. 10, a clock signal 1010 represents a referencesignal for generating output signal r(t). Clock signal 1010 is of thesame frequency as that of desired output signal r(t).

Referring to FIG. 10, an Iclk_phase signal 1012 and a Qclk_phase signal1014 represent amplitude analog values that are multiplied by thein-phase and quadrature components of Clk signal 1010 and are calculatedfrom the baseband I and Q signals.

Still referring to FIG. 10, clock signal 1010 is multiplied withIclk_phase signal 1012. In parallel, a 90° degrees shifted version ofclock signal 1010 is multiplied with Qclk_phase signal 1014. The twomultiplied signals are combined to generate Rclk signal 1016. Rclksignal 1016 is of the same frequency as clock signal 1010. Further, Rclksignal 1016 is characterized by a phase shift angle according to theratio of Q(t) and I(t). The magnitude of Rclk signal 1016 is such thatR²clk=I²clk_phase+Q²clk_phase. Accordingly, Rclk signal 1016 representsa substantially constant envelope signal having the phasecharacteristics of the desired output signal r(t).

Still referring to FIG. 10, Rclk signal 1016 is input, in parallel, intotwo vector modulators 1060 and 1062. Vector modulators 1060 and 1062generate the U(t) and L(t) substantially constant envelope constituents,respectively, of the desired output signal r(t) as described in (12). Invector modulator 1060, an in-phase Rclk signal 1020, multiplied withCommon signal 1028, is combined with a 90° degree shifted version 1018of Rclk signal, multiplied with first signal 1026. In parallel, invector modulator 1062, an in-phase Rclk signal 1022, multiplied withCommon signal 1028, is combined with a 90° degrees shifted version 1024of Rclk signal, multiplied with second signal 1030. Common signal 1028,first signal 1026, and second signal 1030 correspond, respectively, tothe real part C and the imaginary parts a and 13 described in equation(12).

Output signals 1040 and 1042 of respective vector modulators 1060 and1062 correspond, respectively, to the U(t) and L(t) constant envelopeconstituents of input signal r(t).

As described above, signals 1040 and 1042 are characterized by havingsubstantially equal and constant magnitude envelopes. Accordingly, whensignals 1040 and 1042 are input into corresponding power amplifiers (PA)1044 and 1046, corresponding amplified signals 1048 and 1050 aresubstantially constant envelope signals.

Power amplifiers 1044 and 1046 apply substantially equal poweramplification to signals 1040 and 1042, respectively. In an embodiment,the power amplification level of PAs 1044 and 1046 is set according tothe desired power level of output signal r(t). Further, amplifiedsignals 1048 and 1050 are in-phase relative to each other. Accordingly,when summed together, as shown in FIG. 10, resulting signal 1052corresponds to the desired output signal r(t).

FIG. 10A is another exemplary embodiment 1000A of the CPCP 2-Branch VPAembodiment. Embodiment 1000A represents a Multiple Input Single Output(MISO) implementation of embodiment 1000 of FIG. 10.

In embodiment 1000A, constant envelope signals 1040 and 1042, outputfrom vector modulators 1060 and 1062, are input into MISO PA 1054. MISOPA 1054 is a two-input single-output power amplifier. In an embodiment,MISO PA 1054 may include various elements, such as pre-drivers, drivers,power amplifiers, and process detectors (not shown in FIG. 10A), forexample. Further, MISO PA 1054 is not limited to being a two-input PA asshown in FIG. 10A. In other embodiments, as will be described furtherbelow with reference to FIGS. 51A-H, PA 1054 can have any number ofinputs.

Operation of the CPCP 2-Branch VPA embodiment is depicted in the processflowchart 1100 of FIG. 11.

The process begins at step 1110, which includes receiving a basebandrepresentation of the desired output signal. In an embodiment, thisinvolves receiving in-phase (I) and quadrature (Q) components of thedesired output signal. In another embodiment, this involves receivingmagnitude and phase of the desired output signal.

Step 1120 includes receiving a clock signal set according to a desiredoutput signal frequency of the desired output signal. In the example ofFIG. 10, step 1120 is achieved by receiving clock signal 1010.

Step 1130 includes processing the clock signal to generate a normalizedclock signal having a phase shift angle according to the received I andQ components. In an embodiment, the normalized clock signal is aconstant envelope signal having a phase shift angle according to a ratioof the I and Q components. The phase shift angle of the normalized clockis relative to the original clock signal. In the example of FIG. 10,step 1130 is achieved by multiplying clock signal 1010's in-phase andquadrature components with Iclk_phase 1012 and Qclk_phase 1014 signals,and then summing the multiplied signal to generate Rclk signal 1016.

Step 1140 includes the processing of the I and Q components to generatethe amplitude information required to produce first and secondsubstantially constant envelope constituent signals.

Step 1150 includes processing the amplitude information of step 1140 andthe normalized clock signal Rclk to generate the first and secondconstant envelope constituents of the desired output signal. In anembodiment, step 1150 involves phase shifting the first and secondconstant envelope constituents of the desired output signal by the phaseshift angle of the normalized clock signal. In the example of FIG. 10,step 1150 is achieved by vector modulators 1060 and 1062 modulating Rclksignal 1016 with first signal 1026, second signal 1030, and commonsignal 1028 to generate signals 1040 and 1042.

Step 1160 includes individually amplifying the first and second constantenvelope constituents, and summing the amplified signals to generate thedesired output signal. In an embodiment, the amplification of the firstand second constant envelope constituents is substantially equal andaccording to a desired power level of the desired output signal. In theexample of FIG. 10, step 1160 is achieved by PAs 1044 and 1046amplifying signals 1040 and 1042 to generate amplified signals 1048 and1050.

FIG. 12 is a block diagram that illustrates an exemplary embodiment of avector power amplifier 1200 implementing the process flowchart 1100.Optional components are illustrated with dashed lines, although in otherembodiments more or less components may be optional.

Referring to FIG. 12, in-phase (I) and quadrature (Q) information signal1210 is received by an I and Q Data Transfer Function module 1216. In anembodiment, I and Q Data Transfer Function 1216 samples signal 1210according to a sample clock 1212. I and Q information signal 1210includes baseband I and Q information of a desired output signal r(t).

In an embodiment, I and Q Data Transfer Function module 1216 processesinformation signal 1210 to generate information signals 1220, 1222,1224, and 1226. The operation of I and Q Data Transfer Function module1216 is further described below in section 3.4.

Referring to FIG. 12, information signal 1220 includes quadratureamplitude information of first and second constant envelope constituentsof a baseband version of desired output signal r(t). With reference toFIG. 9A, for example, information signal 1220 includes the α and βquadrature components. Referring again to FIG. 12, information signal1226 includes in-phase amplitude information of the first and secondconstant envelope constituents of the baseband version of signal r(t).With reference to FIG. 9A, for example, information signal 1226 includesthe common C in-phase component.

Still referring to FIG. 12, information signals 1222 and 1224 includenormalized in-phase Iclk_phase and quadrature Qclk_phase signals,respectively. Iclk_phase and Qclk_phase are normalized versions of the Iand Q information signals included in signal 1210. In an embodiment,Iclk_phase and Qclk_phase are normalized such that that(I²clk_phase+Q²clk_phase=constant). It is noted that the phase of signal1250 corresponds to the phase of the desired output signal and iscreated from Iclk_phase and Qclk_phase. Referring to FIG. 9B, Iclk_phaseand Qclk_phase are related to I and Q as follows:

$\begin{matrix}{\theta = {{\tan^{- 1}( \frac{Q}{I} )} = {\tan^{- 1}( \frac{Q_{clk\_ phase}}{I_{clk\_ phase}} )}}} & (12.1)\end{matrix}$

where θ represents the phase of the desired output signal, represented bphasor {right arrow over (R_(out))} in FIG. 9B. The sign information ofthe baseband I and Q information must be taken into account to calculateθ for all four quadrants.

In the exemplary embodiment of FIG. 12, information signals 1220, 1222,1224, and 1226 are digital signals. Accordingly, each of signals 1220,1222, 1224, and 1226 is fed into a corresponding digital-to-analogconverter (DAC) 1230, 1232, 1234, and 1236. The resolution and samplerate of DACs 1230, 1232, 1234, and 1236 is selected according tospecific signaling schemes. DACs 1230, 1232, 1234, and 1236 arecontrolled by DAC clock signals 1221, 1223, 1225, and 1227,respectively. DAC clock signals 1221, 1223, 1225, and 1227 may bederived from a same clock signal or may be independent.

In other embodiments, information signals 1220, 1222, 1224, and 1226 aregenerated in analog format and no DACs are required.

Referring to FIG. 12, DACs 1230, 1232, 1234, and 1236 convert digitalinformation signals 1220, 1222, 1224, and 1226 into corresponding analogsignals, and input these analog signal into optional interpolationfilters 1231, 1233, 1235, and 1237, respectively. Interpolation filters1231, 1233, 1235, and 1237, which also serve as anti-aliasing filters,shape the DACs output signals to produce the desired output waveform.Interpolation filters 1231, 1233, 1235, and 1237 generate signals 1240,1244, 1246, and 1248, respectively. Signal 1242 represents the inverseof signal 1240.

Still referring to FIG. 12, signals 1244 and 1246, which includeIclk_phase and Qclk_phase information, are input into a vector modulator1238. Vector modulator 1238 multiplies signal 1244 with a channel clocksignal 1214. Channel clock signal 1214 is selected according to adesired output signal frequency. In parallel, vector modulator 1238multiplies signal 1246 with a 90° shifted version of channel clocksignal 1214. In other words, vector modulator 1238 generates an in-phasecomponent having amplitude of Iclk_phase and a quadrature componenthaving amplitude of Qclk_phase.

Vector modulator 1238 combines the two modulated signals to generateRclk signal 1250. Rclk signal 1250 is a substantially constant envelopesignal having the desired output frequency and a phase shift angleaccording to the I and Q data included in signal 1210.

Still referring to FIG. 12, signals 1240, 1242, and 1248 include the U,L, and Common C amplitude components, respectively, of the complexenvelope of signal r(t). Signals 1240, 1242, and 1248 along with Rclksignal 1250 are input into vector modulators 1260 and 1262.

Vector modulator 1260 combines signal 1240, multiplied with a 90°shifted version of Rclk signal 1250, and signal 1248, multiplied with a0° shifted version of Rclk signal 1250, to generate output signal 1264.In parallel, vector modulator 1262 combines signal 1242, multiplied witha 90° shifted version of Rclk signal 1250, and signal 1248, modulatedwith a 0° shifted version of Rclk signal 1250, to generate output signal1266.

Output signals 1264 and 1266 represent substantially constant envelopesignals. Further, phase shifts of output signals 1264 and 1266 relativeto Rclk signal 1250 are determined by the angle relationships associatedwith the ratios α/C and β/C, respectively. In an embodiment, α=−β andtherefore output signals 1264 and 1266 are symmetrically phased relativeto Rclk signal 1250. With reference to FIG. 9B, for example, outputsignals 1264 and 1266 correspond, respectively, to the {right arrow over(U)} and {right arrow over (L)} constant magnitude phasors.

A sum of output signals 1264 and 1266 results in achannel-clock-modulated signal having the I and Q characteristics ofbaseband signal r(t). To achieve a desired power level at the output ofvector power amplifier 1200, however, signals 1264 and 1266 areamplified to generate an amplified output signal. In the embodiment ofFIG. 12, signals 1264 and 1266 are, respectively, input into poweramplifiers (PAs) 1270 and 1272 and amplified. In an embodiment, PAs 1270and 1272 include switching power amplifiers. Autobias circuitry 1218controls the bias of PAs 1270 and 1272 as further described below insection 3.5.2. In the embodiment of FIG. 12, for example, autobiascircuitry 1218 provides a bias voltage 1228 to PAs 1270 and 1272.

In an embodiment, PAs 1270 and 1272 apply substantially equal poweramplification to respective constant envelope signals 1264-1266. In anembodiment, the power amplification is set according to the desiredoutput power level. In other embodiments of vector power amplifier 1200,PA drivers and/or pre-drivers are additionally employed to provideadditional power amplification capability to the amplifier. In theembodiment of FIG. 12, for example, PA drivers 1284 and 1286 areoptionally added, respectively, between vector modulators 1260 and 1262and subsequent PAs 1270 and 1272.

Respective output signals 1274 and 1276 of PAs 1270 and 1272 aresubstantially constant envelope signals. Further, when output signals1274 and 1276 are summed, the resulting signal has minimal non-lineardistortion. In the embodiment of FIG. 12, output signals 1274 and 1276are coupled together to generate output signal 1280 of vector poweramplifier 1200. In an embodiment, no isolation is used in coupling theoutputs of PAs 1270 and 1272. Accordingly, minimal power loss isincurred by the coupling. In an embodiment, the outputs of PAs 1270 and1272 are directly coupled together using a wire. Direct coupling in thismanner means that there is minimal or no resistive, inductive, orcapacitive isolation between the outputs of PAs 1270 and 1272. In otherwords, outputs of PAs 1270 and 1272 are coupled together withoutintervening components. Alternatively, in an embodiment, the outputs ofPAs 1270 and 1272 are coupled together indirectly through inductancesand/or capacitances that result in low or minimal impedance connections,and/or connections that result in minimal isolation and minimal powerloss. Alternatively, outputs of PAs 1270 and 1272 are coupled using wellknown combining techniques, such as Wilkinson, hybrid combiners,transformers, or known active combiners. In an embodiment, the PAs 1270and 1272 provide integrated amplification and power combining in asingle operation. In an embodiment, one or more of the power amplifiersand/or drivers described herein are implemented using multiple input,single output power amplification techniques, examples of which areshown in FIGS. 12A, 12B, and 51A-H.

Output signal 1280 represents a signal having the I and Qcharacteristics of baseband signal r(t) and the desired output powerlevel and frequency. In embodiments of vector power amplifier 1200, apull-up impedance 1288 is coupled between the output of vector poweramplifier 1200 and a power supply. In other embodiments, an impedancematching network 1290 is coupled at the output of vector power amplifier1200. Output stage embodiments according to power amplification methodsand systems of the present invention will be further described below insection 3.5.

In other embodiments of vector power amplifier 1200, process detectorsare employed to compensate for any process variations in circuitry ofthe amplifier. In the exemplary embodiment of FIG. 12, for example,process detector 1282 is optionally added to monitor variations in PAdrivers 1284 and 1286.

FIG. 12A is a block diagram that illustrates another exemplaryembodiment of a vector power amplifier 1200A implementing the processflowchart 1100. Optional components are illustrated with dashed lines,although in other embodiments more or less components may be optional.

Embodiment 1200A illustrates a multiple-input single-output (MISO)implementation of embodiment 1200. In embodiment 1200A, constantenvelope signals 1261 and 1263, output from vector modulators 1260 and1262, are input into MISO PA 1292. MISO PA 1292 is a two-inputsingle-output power amplifier. In an embodiment, MISO PA 1292 includeselements 1270, 1272, 1282, 1284, and 1286 as shown in the embodiment ofFIG. 12. In another embodiment, MISO PA 1292 may include other elements,such as pre-drivers, not shown in the embodiment of FIG. 12. Further,MISO PA 1292 is not limited to being a two-input PA as shown in FIG.12A. In other embodiments as will be described further below withreference to FIGS. 51A-H, PA 1292 can have any number of inputs andoutputs.

Still referring to FIG. 12A, embodiment 1200A illustrates oneimplementation for delivering autobias signals to MISO PA 1292. In theembodiment of FIG. 12A, Autobias signal 1228 generated by Autobiascircuitry 1218, has one or more signals derived from it to biasdifferent stages of MISO PA 1292. As shown in the example of FIG. 12A,three bias control signals Bias A, Bias B, and Bias C are derived fromAutobias signal 1228, and then input at different stages of MISO PA1292. For example, Bias C may be the bias signal to the pre-driver stageof MISO PA 1292. Similarly, Bias B and Bias A may be the bias signals tothe driver and PA stages of MISO PA 1292.

In another implementation, shown in embodiment 1200B of FIG. 12 B,Autobias circuitry 1218 generates separate Autobias signals 1295, 1296,and 1295, corresponding to Bias A, Bias B, and Bias C, respectively.Signals 1295, 1296, and 1297 may or may not be generated separatelywithin Autobias circuitry 1218, but are output separately as shown.Further, signals 1295, 1296, and 1297 may or may not be related asdetermined by the biasing of the different stages of MISO PA 1294.

Other aspects of vector power amplifiers 1200A and 1200B substantiallycorrespond to those described above with respect to vector poweramplifier 1200.

FIG. 13 is a block diagram that illustrates another exemplary embodiment1300 of a vector power amplifier according to the CPCP 2-Branch VPAembodiment. Optional components are illustrated with dashed lines,although in other embodiments more or less components may be optional.

In the exemplary embodiment of FIG. 13, a DAC of sufficient resolutionand sample rate 1320 replaces DACs 1230, 1232, 1234 and 1236 of theembodiment of FIG. 12. DAC 1320 is controlled by a DAC clock 1324.

DAC 1320 receives information signal 1310 from I and Q Data TransferFunction module 1216. Information signal 1310 includes identicalinformation content to signals 1220, 1222, 1224 and 1226 in theembodiment of FIG. 12.

DAC 1320 may output a single analog signal at a time. Accordingly, asample-and-hold architecture may be used as shown in FIG. 13.

DAC 1320 sequentially outputs analog signals 1332, 1334, 1336, 1336 to afirst set of sample-and-hold circuits 1342, 1344, 1346, and 1348. In anembodiment, DAC 1230 is clocked at a sufficient rate to replace DACs1230, 1232, 1234, and 1236 of the embodiment of FIG. 12. An outputselector 1322 determines which of output signals 1332, 1334, 1336, and1338 should be selected for output.

DAC 1320's DAC clock signal 1324, output selector signal 1322, andsample-and-hold clocks 1340A-D and 1350 are controlled by a controlmodule that can be independent or integrated into transfer functionmodule 1216.

In an embodiment, sample-and-hold circuits (S/H) 1342, 1344, 1346, and1348 hold the received analog values and, according to a clock signal1340A-D, release the values to a second set of sample-and-hold circuits1352, 1354, 1356, and 1358. For example, S/H 1342 release its value toS/H 1352 according to a received clock signal 1340A. In turn,sample-and-hold circuits 1352, 1354, 1356, and 1358 hold the receivedanalog values, and simultaneously release the values to interpolationfilters 1231, 1233, 1235, and 1237 according to a common clock signal1350. A common clock signal 1350 is used in order to ensure that theoutputs of S/H 1352, 1354, 1356, and 1358 are time-aligned.

In another embodiment, a single layer of S/H circuitry that includes S/H1342, 1344, 1346, and 1348 can be employed. Accordingly, S/H circuits1342, 1344, 1346, and 1348 receive analog values from DAC 1320, and eachreleases its received value according to a clock independent of theothers. For example, S/H 1342 is controlled by clock 1340A, which maynot be synchronized with clock 1340B that controls S/H 1344. To ensurethat outputs of S/H circuits 1342, 1344, 1346, and 1348 aretime-aligned, delays between clocks 1340A-D are pre-compensated for inprior stages of the amplifier. For example, DAC 1320 outputs signal1332, 1334, 1336, and 1338 with appropriately selected delays to S/Hcircuits 1342, 1344, 1346, and 1348 in order to compensate for the timedifferences between clocks 1340A-D.

Other aspects of vector power amplifier 1300 are substantiallyequivalent to those described above with respect to vector poweramplifier 1200.

FIG. 13A is a block diagram that illustrates another exemplaryembodiment 1300A of a vector power amplifier according to the CPCP2-Branch VPA embodiment. Optional components are illustrated with dashedlines, although in other embodiments more or less components may beoptional. Embodiment 1300A is a MISO implementation of embodiment 1300of FIG. 13.

In the embodiment of FIG. 13A, constant envelope signals 1261 and 1263output from vector modulators 1260 and 1262 are input into MISO PA 1360.MISO PA 1360 is a two-input single-output power amplifier. In anembodiment, MISO PA 1360 includes elements 1270, 1272, 1282, 1284, and1286 as shown in the embodiment of FIG. 13. In another embodiment, MISOPA 1360 may include other elements, such as pre-drivers, not shown inthe embodiment of FIG. 13, or functional equivalents thereof. Further,MISO PA 1360 is not limited to being a two-input PA as shown in FIG.13A. In other embodiments as will be described further below withreference to FIGS. 51A-H, PA 1360 can have any number of inputs.

The embodiment of FIG. 13A further illustrates two different sample andhold architectures with a single or two levels of S/H circuitry asshown. The two implementations have been described above with respect toFIG. 13.

Embodiment 1300A also illustrates optional bias control circuitry 1218and associated bias control signal 1325, 1326, and 1327. Signals 1325,1326, and 1327 may be used to bias different stages of MISO PA 1360 incertain embodiments.

Other aspects of vector power amplifier 1300A are equivalent to thosedescribed above with respect to vector power amplifiers 1200 and 1300.

3.3) Direct Cartesian 2-Branch Vector Power Amplifier

A Direct Cartesian 2-Branch VPA embodiment shall now be described. Thisname is used herein for reference purposes, and is not functionally orstructurally limiting.

According to the Direct Cartesian 2-Branch VPA embodiment, atime-varying envelope signal is decomposed into two constant envelopeconstituent signals. The constituent signals are individually amplifiedequally or substantially equally, and then summed to construct anamplified version of the original time-varying envelope signal.

In one embodiment of the Direct Cartesian 2-Branch VPA embodiment, amagnitude and a phase angle of a time-varying envelope signal arecalculated from in-phase and quadrature components of an input signal.Using the magnitude and phase information, in-phase and quadratureamplitude components are calculated for two constant envelopeconstituents of the time-varying envelope signal. The two constantenvelope constituents are then generated, amplified equally orsubstantially equally, and summed to generate an amplified version ofthe original time-varying envelope signal R_(in).

The concept of the Direct Cartesian 2-Branch VPA will now be describedwith reference to FIGS. 9A and 14.

As described and verified above with respect to FIG. 9A, the phasor{right arrow over (R′)} can be obtained by the sum of an upper phasor{right arrow over (U′)} and a lower phasor {right arrow over (L′)}appropriately phased to produce {right arrow over (R′)}. {right arrowover (R′)} is calculated to be proportional to the magnitude R_(in).Further, {right arrow over (U′)} and {right arrow over (L′)} can bemaintained to have substantially constant magnitude. In the time domain,{right arrow over (U′)} and {right arrow over (L′)} represent twosubstantially constant envelope signals. The time domain equivalentr′(t) of {right arrow over (R′)} can thus be obtained, at any timeinstant, by the sum of two substantially constant envelope signals.

For the case illustrated in FIG. 9A, the phase shift of {right arrowover (U′)} and {right arrow over (L′)} relative to {right arrow over(R′)}, illustrated as angle φ/2 in FIG. 9A, is related to the magnitudeof {right arrow over (R′)} as follows:

$\begin{matrix}{\frac{\varphi}{2} = {\cos^{- 1}( \frac{R}{2\sqrt{1 - \frac{R^{2}}{4}}} )}} & (13)\end{matrix}$

where R represents the normalized magnitude of phasor {right arrow over(R′)}.

In the time domain, it was shown that a time-varying envelope signal,r′(t)=R(t) cos(ωt) for example, can be constructed by the sum of twoconstant envelope signals as follows:

r′(t)=U′(t)+L′(t);

U′(t)=C×cos(ωt)+α×sin(ωt);

L′(t)=C×cos(ωt)−β×sin(ωt).  (14)

where C denotes the in-phase amplitude component of phasors {right arrowover (U′)} and {right arrow over (L′)} and is equal or substantiallyequal to

$A \times {\cos ( \frac{\varphi}{2} )}$

(A being a constant). α and β denote the quadrature amplitude componentsof phasors {right arrow over (U′)} and {right arrow over (L′)},respectively.

$\alpha = {\beta = {A \times {{\sin ( \frac{\varphi}{2} )}.}}}$

Note that equations (14) can be modified for non-sinusoidal signals bychanging the basis function from sinusoidal to the desired function.

FIG. 14 illustrates phasor {right arrow over (R)} and its two constantmagnitude constituent phasors {right arrow over (U)} and {right arrowover (L)}. {right arrow over (R)} is shifted by θ degrees relative to{right arrow over (R′)} in FIG. 9A. Accordingly, it can be verifiedthat:

{right arrow over (R)}={right arrow over (R′)}×e ^(jθ)=({right arrowover (U′)}+{right arrow over (L′)})×e ^(jθ) ={right arrow over(U)}+{right arrow over (L)};

{right arrow over (U)}={right arrow over (U′)}×e ^(jθ);

{right arrow over (L)}={right arrow over (L′)}×e ^(jθ).  (15)

From equations (15), it can be further shown that:

{right arrow over (U)}={right arrow over (U)}×e ^(jθ)=(C+jα)×e ^(jθ);

{right arrow over (U)}=(C+jα)(cos θ+j sin θ)=(C cos θ−α sin θ)+j(C sinθ+α cos θ).  (16)

Similarly, it can be shown that:

{right arrow over (L)}={right arrow over (L′)}×e ^(jθ)=(C+jβ)×e ^(jθ);

{right arrow over (L)}=(C+jβ)(cos θ+j sin θ)=(C cos θ−β sin θ)+j(C sinθ+β cos θ).  (17)

Equations (16) and (17) can be re-written as:

{right arrow over (U)}=(C cos θ−α sin θ)+j(C sin θ+α cos θ)=U _(x) +jU_(y);

{right arrow over (L)}=(C cos θ−β sin θ)+j(C sin θ+β cos θ)=L _(x) +jL_(y).  (18)

Equivalently, in the time domain:

U(t)=U _(x)φ₁(t)+U _(y)φ₂(t);

L(t)=L _(x)φ₁(t)+L _(y)φ₂(t);  (19)

where φ₁(t) and φ₂(t) represent an appropriately selected orthogonalbasis functions.

From equations (18) and (19), it is noted that it is sufficient tocalculate the values of α, β, C and sin(Θ) and cos(Θ) in order todetermine the two constant envelope constituents of a time-varyingenvelope signal r(t). Further, α, β and C can be entirely determinedfrom magnitude and phase information, equivalently I and Q components,of signal r(t).

FIG. 15 is a block diagram that conceptually illustrates an exemplaryembodiment 1500 of the Direct Cartesian 2-Branch VPA embodiment. Anoutput signal r(t) of desired power level and frequency characteristicsis generated from in-phase and quadrature components according to theDirect Cartesian 2-Branch VPA embodiment.

In the example of FIG. 15, a clock signal 1510 represents a referencesignal for generating output signal r(t). Clock signal 1510 is of thesame frequency as that of desired output signal r(t).

Referring to FIG. 15, exemplary embodiment 1500 includes a first branch1572 and a second branch 1574. The first branch 1572 includes a vectormodulator 1520 and a power amplifier (PA) 1550. Similarly, the secondbranch 1574 includes a vector modulator 1530 and a power amplifier (PA)1560.

Still referring to FIG. 15, clock signal 1510 is input, in parallel,into vector modulators 1520 and 1530. In vector modulator 1520, anin-phase version 1522 of clock signal 1510, multiplied with U_(x) signal1526, is summed with a 90° degrees shifted version 1524 of clock signal1510, multiplied with U_(y) signal 1528. In parallel, in vectormodulator 1530, an in-phase version 1532 of clock signal 1510,multiplied with Lx signal 1536, is summed with a 90° degrees shiftedversion 1534 of clock signal 1510, multiplied with Ly signal 1538. U_(x)signal 1526 and U_(y) signal 1528 correspond, respectively, to thein-phase and quadrature amplitude components of the U(t) constantenvelope constituent of signal r(t) provided in equation (19).Similarly, L_(x) signal 1536, and L_(y) signal 1538 correspond,respectively, to the in-phase and quadrature amplitude components of theL(t) constant envelope constituent of signal r(t) provided in equation(19).

Accordingly, respective output signals 1540 and 1542 of vectormodulators 1520 and 1530 correspond, respectively, to the U(t) and L(t)constant envelope constituents of signal r(t) as described above inequations (19). As described above, signals 1540 and 1542 arecharacterized by having equal and constant or substantially equal andconstant magnitude envelopes.

Referring to FIG. 15, to generate the desired power level of outputsignal r(t), signals 1540 and 1542 are input into corresponding poweramplifiers 1550 and 1560.

In an embodiment, power amplifiers 1550 and 1560 apply equal orsubstantially equal power amplification to signals 1540 and 1542,respectively. In an embodiment, the power amplification level of PAs1550 and 1560 is set according to the desired power level of outputsignal r(t).

Amplified output signals 1562 and 1564 are substantially constantenvelope signals. Accordingly, when summed together, as shown in FIG.15, resulting signal 1570 corresponds to the desired output signal r(t).

FIG. 15A is another exemplary embodiment 1500A of the Direct Cartesian2-Branch VPA embodiment. Embodiment 1500A represents a Multiple InputSignal Output (MISO) implementation of embodiment 1500 of FIG. 15.

In embodiment 1500A, constant envelope signals 1540 and 1542, outputfrom vector modulators 1520 and 1530, are input into MISO PA 1580. MISOPA 1580 is a two-input single-output power amplifier. In an embodiment,MISO PA 1580 may include various elements, such as pre-drivers, drivers,power amplifiers, and process detectors (not shown in FIG. 15A), forexample. Further, MISO PA 1580 is not limited to being a two-input PA asshown in FIG. 15A. In other embodiments, as will be described furtherbelow with reference to FIGS. 51A-H, PA 1580 can have any number ofinputs.

Operation of the Direct Cartesian 2-Branch VPA embodiment is depicted inthe process flowchart 1600 of FIG. 16. The process begins at step 1610,which includes receiving a baseband representation of a desired outputsignal. In an embodiment, the baseband representation includes I and Qcomponents. In another embodiment, the I and Q components are RFcomponents that are down-converted to baseband.

Step 1620 includes receiving a clock signal set according to a desiredoutput signal frequency of the desired output signal. In the example ofFIG. 15, step 1620 is achieved by receiving clock signal 1510.

Step 1630 includes processing the I and Q components to generatein-phase and quadrature amplitude information of first and secondconstant envelope constituent signals of the desired output signal. Inthe example of FIG. 15, the in-phase and quadrature amplitudeinformation is illustrated by U_(x), U_(y), L_(x), and L_(y).

Step 1640 includes processing the amplitude information and the clocksignal to generate the first and second constant envelope constituentsignals of the desired output signal. In an embodiment, the first andsecond constant envelope constituent signals are modulated according tothe desired output signal frequency. In the example of FIG. 15, step1640 is achieved by vector modulators 1520 and 1530, clock signal 1510,and amplitude information signals 1526, 1528, 1536, and 1538 to generatesignals 1540 and 1542.

Step 1650 includes amplifying the first and second constant envelopeconstituents, and summing the amplified signals to generate the desiredoutput signal. In an embodiment, the amplification of the first andsecond constant envelope constituents is according to a desired powerlevel of the desired output signal. In the example of FIG. 15, step 1650is achieved by PAs 1550 and 1560 amplifying respective signals 1540 and1542 and, subsequently, by the summing of amplified signals 1562 and1564 to generate output signal 1574.

FIG. 17 is a block diagram that illustrates an exemplary embodiment of avector power amplifier 1700 implementing the process flowchart 1600.Optional components are illustrated with dashed lines, although otherembodiments may have more or less optional components.

Referring to FIG. 17, in-phase (I) and quadrature (Q) information signal1710 is received by an I and Q Data Transfer Function module 1716. In anembodiment, I and Q Data Transfer Function module 1716 samples signal1710 according to a sample clock 1212. I and Q information signal 1710includes baseband I and Q information.

In an embodiment, I and Q Data Transfer Function module 1716 processesinformation signal 1710 to generate information signals 1720, 1722,1724, and 1726. The operation of I and Q Data Transfer Function module1716 is further described below in section 3.4.

Referring to FIG. 17, information signal 1720 includes vector modulator1750 quadrature amplitude information that is processed through DAC 1730to generate signal 1740. Information signal 1722 includes vectormodulator 1750 in-phase amplitude information that is processed throughDAC 1732 to generate signal 1742. Signals 1740 and 1742 are calculatedto generate a substantially constant envelope signal 1754. Withreference to FIG. 14, for example, information signals 1720 and 1722include the upper quadrature and in-phase components U_(y) and U_(x),respectively.

Still referring to FIG. 17, information signal 1726 includes vectormodulator 1752 quadrature amplitude information that is processedthrough DAC 1736 to generate signal 1746. Information signal 1724includes vector modulator 1752 in-phase amplitude information that isprocessed through DAC 1734 to generate signal 1744. Signals 1744 and1746 are calculated to generate a substantially constant envelope signal1756. With reference to FIG. 14, for example, information signals 1724and 1726 include the lower in-phase and quadrature components L_(x) andL_(y), respectively.

In the exemplary embodiment of FIG. 17, information signals 1720, 1722,1724 and 1726 are digital signals. Accordingly, each of signals 1720,1722, 1724 and 1726 is fed into a corresponding digital-to-analogconverter (DAC) 1730, 1732, 1734, and 1736. The resolution and samplerates of DACs 1730, 1732, 1734, and 1736 are selected according to thespecific desired signaling schemes. DACs 1730, 1732, 1734, and 1736 arecontrolled by DAC clock signals 1721, 1723, 1725, and 1727,respectively. DAC clock signals 1721, 1723, 1725, and 1727 may bederived from a same clock or may be independent of each other.

In other embodiments, information signals 1720, 1722, 1724 and 1726 aregenerated in analog format and no DACs are required.

Referring to FIG. 17, DACs 1730, 1732, 1734, and 1736 convert digitalinformation signals 1720, 1722, 1724, and 1726 into corresponding analogsignals, and input these analog signals into optional interpolationfilters 1731, 1733, 1735, and 1737, respectively. Interpolation filters1731, 1733, 1735, and 1737, which also serve as anti-aliasing filters,shape the DACs output signals to produce the desired output waveform.Interpolation filters 1731, 1733, 1735, and 1737 generate signals 1740,1742, 1744, and 1746, respectively.

Still referring to FIG. 17, signals 1740, 1742, 1744, and 1746 are inputinto vector modulators 1750 and 1752. Vector modulators 1750 and 1752generate first and second constant envelope constituents. In theembodiment of FIG. 17, channel clock 1714 is set according to a desiredoutput signal frequency to thereby establish the frequency of the outputsignal 1770.

Referring to FIG. 17, vector modulator 1750 combines signal 1740,multiplied with a 90° shifted version of channel clock signal 1714, andsignal 1742, multiplied with a 0° shifted version of channel clocksignal 1714, to generate output signal 1754. In parallel, vectormodulator 1752 combines signal 1746, multiplied with a 90° shiftedversion of channel clock signal 1714, and signal 1744, multiplied with a0° shifted version of channel clock signal 1714, to generate outputsignal 1756.

Output signals 1754 and 1756 represent constant envelope signals. A sumof output signals 1754 and 1756 results in a carrier signal having the Iand Q characteristics of the original baseband signal. In embodiments,to generate a desired power level at the output of vector poweramplifier 1700, signals 1754 and 1756 are amplified and then summed. Inthe embodiment of FIG. 17, for example, signals 1754 and 1756 are,respectively, input into corresponding power amplifiers (PAs) 1760 and1762. In an embodiment, PAs 1760 and 1762 include switching poweramplifiers. Autobias circuitry 1718 controls the bias of PAs 1760 and1762. In the embodiment of FIG. 17, for example, autobias circuitry 1718provides a bias voltage 1728 to PAs 1760 and 1762.

In an embodiment, PAs 1760 and 1762 apply equal or substantially equalpower amplification to respective constant envelope signals 1754 and1756. In an embodiment, the power amplification is set according to thedesired output power level. In other embodiments of vector poweramplifier 1700, PA drivers are additionally employed to provideadditional power amplification capability to the amplifier. In theembodiment of FIG. 17, for example, PA drivers 1774 and 1776 areoptionally added, respectively, between vector modulators 1750 and 1752and subsequent PAs 1760 and 1762.

Respective output signals 1764 and 1766 of PAs 1760 and 1762 aresubstantially constant envelope signals. In the embodiment of FIG. 17,output signals 1764 and 1766 are coupled together to generate outputsignal 1770 of vector power amplifier 1700. In embodiments, it is notedthat the outputs of PAs 1760 and 1762 are directly coupled. Directcoupling in this manner means that there is minimal or no resistive,inductive, or capacitive isolation between the outputs of PAs 1760 and1762. In other words, outputs of PAs 1760 and 1762 are coupled togetherwithout intervening components. Alternatively, in an embodiment, theoutputs of PAs 1760 and 1762 are coupled together indirectly throughinductances and/or capacitances that result in low or minimal impedanceconnections, and/or connections that result in minimal isolation andminimal power loss. Alternatively, outputs of PAs 1760 and 1762 arecoupled using well known combining techniques, such as Wilkinson, hybridcouplers, transformers, or known active combiners. In an embodiment, thePAs 1760 and 1762 provide integrated amplification and power combiningin a single operation. In an embodiment, one or more of the poweramplifiers and/or drivers described herein are implemented usingmultiple input, single output (MISO) power amplification techniques,examples of which are shown in FIGS. 17A, 17B, and 51A-H.

Output signal 1770 represents a signal having the desired I and Qcharacteristics of the baseband signal and the desired output powerlevel and frequency. In embodiments of vector power amplifier 1700, apull-up impedance 1778 is coupled between the output of vector poweramplifier 1700 and a power supply. In other embodiments, an impedancematching network 1780 is coupled at the output of vector power amplifier1700. Output stage embodiments according to power amplification methodsand systems of the present invention will be further described below insection 3.5.

In other embodiments of vector power amplifier 1700, process detectorsare employed to compensate for any process and/or temperature variationsin circuitry of the amplifier. In the exemplary embodiment of FIG. 17,for example, process detector 1772 is optionally added to monitorvariations in PA drivers 1774 and 1776.

FIG. 17A is a block diagram that illustrates another exemplaryembodiment 1700A of a vector power amplifier implementing processflowchart 1600. Optional components are illustrated with dashed lines,although other embodiments may have more or less optional components.Embodiment 1700A illustrates a multiple-input single-output (MISO)implementation of the amplifier of FIG. 17. In the embodiment of FIG.17A, constant envelope signals 1754 and 1756, output from vectormodulators 1750 and 1760, are input into MISO PA 1790. MISO PA 1790 is atwo-input single-output power amplifier. In an embodiment, MISO PA 1790include elements 1760, 1762, 1772, 1774, and 1776 as shown in theembodiment of FIG. 17, or functional equivalents thereof. In anotherembodiment, MISO PA 1790 may include other elements, such aspre-drivers, not shown in the embodiment of FIG. 17. Further, MISO PA1790 is not limited to being a two-input PA as shown in FIG. 17A. Inother embodiments, as will be described further below with reference toFIGS. 51A-H, PA 1790 can have any number of inputs.

In another embodiment of embodiment 1700, shown as embodiment 1700B ofFIG. 17B, optional Autobias circuitry 1218 generates separate biascontrol signals 1715, 1717, and 1719, corresponding to Bias A, Bias B,and Bias C, respectively. Signals 1715, 1717, and 1719 may or may not begenerated separately within Autobias circuitry 1718, but are outputseparately as shown. Further, signals 1715, 1717, and 1719 may or maynot be related as determined by the biasing required for the differentstages of MISO PA 1790.

FIG. 18 is a block diagram that illustrates another exemplary embodiment1800 of a vector power amplifier according to the Direct Cartesian2-Branch VPA embodiment of FIG. 16. Optional components are illustratedwith dashed lines, although other embodiments may have more or lessoptional components.

In the exemplary embodiment of FIG. 18, a DAC 1820 of sufficientresolution and sample rate replaces DACs 1730, 1732, 1734, and 1736 ofthe embodiment of FIG. 17. DAC 1820 is controlled by a DAC clock 1814.

DAC 1820 receives information signal 1810 from I and Q Data TransferFunction module 1716. Information signal 1810 includes identicalinformation content to signals 1720, 1722, 1724, and 1726 in theembodiment of FIG. 17.

DAC 1820 may output a single analog signal at a time. Accordingly, asample-and-hold architecture may be used as shown in FIG. 18.

In the embodiment of FIG. 18, DAC 1820 sequentially outputs analogsignals 1822, 1824, 1826, and 1828 to sample-and-hold circuits 1832,1834, 1836, and 1838, respectively. In an embodiment, DAC 1820 is ofsufficient resolution and sample rate to replace DACs 1720, 1722, 1724,and 1726 of the embodiment of FIG. 17. An output selector 1812determines which of output signals 1822, 1824, 1826, and 1828 areselected for output.

DAC 1820's DAC clock signal 1814, output selector signal 1812, andsample-and-hold clocks 1830A-D, and 1840 are controlled by a controlmodule that can be independent or integrated into transfer functionmodule 1716.

In an embodiment, sample-and-hold circuits 1832, 1834, 1836, and 1838sample and hold their respective values and, according to a clock signal1830A-D, release the values to a second set of sample-and-hold circuits1842, 1844, 1846, and 1848. For example, S/H 1832 release's its value toS/H 1842 according to a received clock signal 1830A. In turn,sample-and-hold circuits 1842, 1844, 1846, and 1848 hold the receivedanalog values, and simultaneously release the values to interpolationfilters 1852, 1854, 1856, and 1858 according to a common clock signal1840.

In another embodiment, a single set of S/H circuitry that includes S/H1832, 1834, 1836, and 1838 can be employed. Accordingly, S/H circuits1832, 1834, 1836, and 1838 receive analog values from DAC 1820, and eachsamples and holds its received value according to independent clocks1830A-D. For example, S/H 1832 is controlled by clock 1830A, which maynot be synchronized with clock 1830B that controls S/H 1834. Forexample, DAC 1820 outputs signals 1822, 1824, 1826, and 1828 withappropriately selected analog values calculated by transfer functionmodule 1716 to S/H circuits 1832, 1834, 1836, and 1838 in order tocompensate for the time differences between clocks 1830A-D.

Other aspects of vector power amplifier 1800 correspond substantially tothose described above with respect to vector power amplifier 1700.

FIG. 18A is a block diagram that illustrates another exemplaryembodiment 1800A of a vector power amplifier according to the DirectCartesian 2-Branch VPA embodiment. Optional components are illustratedwith dashed lines, although in other embodiments more or less componentsmay be optional. Embodiment 1800A is a Multiple Input Single Output(MISO) implementation of embodiment 1800 of FIG. 18.

In the embodiment of FIG. 18A, constant envelope signals 1754 and 1756,output from vector modulators 1750 and 1752, are input into MISO PA1860. MISO PA 1860 is a two-input single-output power amplifier. In anembodiment, MISO PA 1860 includes elements 1744, 1746, 1760, 1762, and1772 as shown in the embodiment of FIG. 18, or functional equivalentsthereof. In another embodiment, MISO PA 1860 may include other elements,such as pre-drivers, not shown in the embodiment of FIG. 17. Further,MISO PA 1860 is not limited to being a two-input PA as shown in FIG.18A. In other embodiments as will be described further below withreference to FIGS. 51A-H, PA 1860 can have any number of inputs.

The embodiment of FIG. 18A further illustrates two different sample andhold architectures with a single or two levels of S/H circuitry asshown. The two implementations have been described above with respect toFIG. 18.

Other aspects of vector power amplifier 1800A are substantiallyequivalent to those described above with respect to vector poweramplifiers 1700 and 1800.

3.4) I and Q Data to Vector Modulator Transfer Functions

In some of the above described embodiments, I and Q data transferfunctions are provided to transform received I and Q data into amplitudeinformation inputs for subsequent stages of vector modulation andamplification. For example, in the embodiment of FIG. 17, I and Q DataTransfer Function module 1716 processes I and Q information signal 1710to generate in-phase and quadrature amplitude information signals 1720,1722, 1724, and 1726 of first and second constant envelope constituents1754 and 1756 of signal r(t). Subsequently, vector modulators 1750 and1752 utilize the generated amplitude information signals 1720, 1722,1724, and 1726 to create the first and second constant envelopeconstituent signals 1754 and 1756. Other examples include modules 710,712, and 1216 in FIGS. 7, 8, 12, and 13. These modules implementtransfer functions to transform I and/or Q data into amplitudeinformation inputs for subsequent stages of vector modulation andamplification.

According to the present invention, I and Q Data Transfer Functionmodules may be implemented using digital circuitry, analog circuitry,software, firmware or any combination thereof.

Several factors affect the actual implementation of a transfer functionaccording to the present invention, and vary from embodiment toembodiment. In one aspect, the selected VPA embodiment governs theamplitude information output of the transfer function and associatedmodule. It is apparent, for example, that I and Q Data Transfer Functionmodule 1216 of the CPCP 2-Branch VPA embodiment 1200 differs in outputthan I and Q Data Transfer Function module 1716 of the Direct Cartesian2-Branch VPA embodiment 1700.

In another aspect, the complexity of the transfer function variesaccording to the desired modulation scheme(s) that need to be supportedby the VPA implementation. For example, the sample clock, the DAC samplerate, and the DAC resolution are selected in accordance with theappropriate transfer function to construct the desired outputwaveform(s).

According to the present invention, transfer function embodiments may bedesigned to support one or more VPA embodiments with the ability toswitch between the supported embodiments as desired. Further, transferfunction embodiments and associated modules can be designed toaccommodate a plurality of modulation schemes. A person skilled in theart will appreciate, for example, that embodiments of the presentinvention may be designed to support a plurality of modulation schemes(individually or in combination) including, but not limited to, BPSK,QPSK, OQPSK, DPSK, CDMA, WCDMA, W-CDMA, GSM, EDGE, MPSK, MQAM, MSK,CPSK, PM, FM, OFDM, and multi-tone signals. In an embodiment, themodulation scheme(s) may be configurable and/or programmable via thetransfer function module.

3.4.1) Cartesian 4-Branch VPA Transfer Function

FIG. 19 is a process flowchart 1900 that illustrates an example I and Qtransfer function embodiment according to the Cartesian 4-Branch VPAembodiment. The process begins at step 1910, which includes receiving anin-phase data component and a quadrature data component. In theCartesian 4-Branch VPA embodiment of FIG. 7A, for example, this isillustrated by I Data Transfer Function module 710 receiving Iinformation signal 702, and Q Data Transfer Function module 712receiving Q information signal 704. It is noted that, in the embodimentof FIG. 7A, I and Q Data Transfer Function modules 710 and 712 areillustrated as separate components. In implementation, however, I and QData Transfer Function modules 710 and 712 may be separate or combinedinto a single module.

Step 1920 includes calculating a phase shift angle between first andsecond substantially equal and constant envelope constituents of the Icomponent. In parallel, step 1920 also includes calculating a phaseshift angle between first and second substantially equal and constantenvelope constituents of the Q component. As described above, the firstand second constant envelope constituents of the I components areappropriately phased relative to the I component. Similarly, the firstand second constant envelope constituents of the Q components areappropriately phased relative to the Q component. In the embodiment ofFIG. 7A, for example, step 1920 is performed by I and Q Data TransferFunction modules 710 and 712.

Step 1930 includes calculating in-phase and quadrature amplitudeinformation associated with the first and second constant envelopeconstituents of the I component. In parallel, step 1930 includescalculating in-phase and quadrature amplitude information associatedwith the first and second constant envelope constituents of the Qcomponent. In the embodiment of FIG. 7A, for example, step 1930 isperformed by and I and Q Data Transfer Function modules 710 and 712.

Step 1940 includes outputting the calculated amplitude information to asubsequent vector modulation stage. In the embodiment of FIG. 7A, forexample, I and Q Transfer Function modules 710 and 712 output amplitudeinformation signals 722, 724, 726, and 728 to vector modulators 760,762, 764, and 766 through DACs 730, 732, 734, and 736.

FIG. 20 is a block diagram that illustrates an exemplary embodiment 2000of a transfer function module, such as transfer function modules 710 and712 of FIG. 7A, implementing the process flowchart 1900. In the exampleof FIG. 20, transfer function module 2000 receives I and Q data signals2010 and 2012. In an embodiment, I and Q data signals 2010 and 2012represent I and Q data components of a baseband signal, such as signals702 and 704 in FIG. 7A.

Referring to FIG. 20, in an embodiment, transfer function module 2000samples I and Q data signals 2010 and 2012 according to a sampling clock2014. Sampled I and Q data signals are received by components 2020 and2022, respectively, of transfer function module 2000. Components 2020and 2022 measure, respectively, the magnitudes of the sampled I and Qdata signals. In an embodiment, components 2020 and 2022 are magnitudedetectors.

Components 2020 and 2022 output the measured I and Q magnitudeinformation to components 2030 and 2032, respectively, of transferfunction module 2000. In an embodiment, the measured I and Q magnitudeinformation is in the form of digital signals. Based on the I magnitudeinformation, component 2030 calculates a phase shift angle φ_(I) betweenfirst and second equal and constant or substantially equal and constantenvelope constituents of the sampled I signal. Similarly, based on the Qmagnitude information, component 2032 calculates phase shift angle φ_(Q)between a first and second equal and constant or substantially equal andconstant envelope constituents of the sampled Q signal. This operationshall now be further described.

In the embodiment of FIG. 20, φ_(I) and φ_(Q) are illustrated asfunctions ƒ(|{right arrow over (I)}|) and ƒ(|{right arrow over (Q)}|) ofthe I and Q magnitude signals. In embodiments, functions ƒ(|{right arrowover (I)}|) and ƒ(|{right arrow over (Q)}|) are set according to therelative magnitudes of the baseband I and Q signals respectively.ƒ(|{right arrow over (I)}|) and ƒ(|{right arrow over (Q)}|) according toembodiments of the present invention will be further described below insection 3.4.4.

Referring to FIG. 20, components 2030 and 2032 output the calculatedphase shift information to components 2040 and 2042, respectively. Basedon phase shift angle φ_(I), component 2040 calculates in-phase andquadrature amplitude information of the first and second constantenvelope constituents of the sampled I signal. Similarly, based on phaseshift angle φ_(Q), component 2042 calculates in-phase and quadratureamplitude information of the first and second constant envelopeconstituents of the sampled Q signal. Due to symmetry, in embodiments ofthe invention, calculation is required for 4 values only. In the exampleof FIG. 20, the values are illustrated as sgn(I)×I_(UX), I_(UY), Q_(UX),and sgn(Q)×Q_(UY), as provided in FIG. 5.

Components 2040 and 2042 output the calculated amplitude information tosubsequent stages of the vector power amplifier. In embodiments, each ofthe four calculated values is output separately to a digital-to-analogconverter. As shown in the embodiment of FIG. 7A for example, signals722, 724, 726, and 728 are output separately to DACs 730, 732, 734, and736, respectively. In other embodiments, signals 722, 724, 726, and 728are output into a single DAC as shown in FIGS. 800A and 800B.

3.4.2) CPCP 2-Branch VPA Transfer Function

FIG. 21 is a process flowchart 2100 that illustrates an example I and Qtransfer function embodiment according to the CPCP 2-Branch VPAembodiment. The process begins at step 2110, which includes receivingin-phase (I) and quadrature (Q) data components of a baseband signal. Inthe CPCP 2-Branch VPA embodiment of FIG. 12, for example, this isillustrated by I and Q Data Transfer Function module 1216 receiving Iand Q information signal 1210.

Step 2120 includes determining the magnitudes |I| and |Q| of thereceived I and Q data components.

Step 2130 includes calculating a magnitude |R| of the baseband signalbased on the measured |I| and |Q| magnitudes. In an embodiment, |R| issuch that |R|²=|I|²+|Q|². In the embodiment of FIG. 12, for example,steps 2120 and 2130 are performed by I and Q Data Transfer Functionmodule 1216 based on received information signal 1210.

Step 2140 includes normalizing the measured |I| and |Q| magnitudes. Inan embodiment, |I| and |Q| are normalized to generate an Iclk_phase andQclk_phase signals (as shown in FIG. 10) such that |I_(clk) _(—)_(phase)|²+|Q_(clk) _(—) _(phase)|²=constant. In the embodiment of FIG.12, for example, step 2140 is performed by I and Q Data TransferFunction module 1216 based on received information signal 1210.

Step 2150 includes calculating in-phase and quadrature amplitudeinformation associated with first and second constant envelopeconstituents. In the embodiment of FIG. 12, for example, step 2150 isperformed by I and Q Data Transfer Function module 1216 based on theenvelope magnitude |R|.

Step 2160 includes outputting the generated Iclk_phase and Qclk_phase(from step 2140) and the calculated amplitude information (from step2150) to appropriate vector modulators. In the embodiment of FIG. 12,for example, I and Q Data Transfer Function module 1216 outputinformation signals 1220, 1222, 1224, and 1226 to vector modulators1238, 1260, and 1262 through DACs 1230, 1232, 1234, and 1236.

FIG. 22 is a block diagram that illustrates an exemplary embodiment 2200of a transfer function module (such as module 1216 of FIG. 12)implementing the process flowchart 2100. In the example of FIG. 22,transfer function module 2200 receives I and Q data signal 2210. In anembodiment, I and Q data signal 2210 includes I and Q components of abaseband signal, such as signal 1210 in the embodiment of FIG. 12, forexample.

In an embodiment, transfer function module 2200 samples I and Q datasignal 2210 according to a sampling clock 2212. Sampled I and Q datasignals are received by component 2220 of transfer function module 2200.Component 2220 measures the magnitudes |{right arrow over (R)}| and|{right arrow over (Q)}| of the sampled I and Q data signals.

Based on the measured |{right arrow over (R)}| and |{right arrow over(Q)}| magnitudes, component 2230 calculates the magnitude |R| of thebaseband signal. In an embodiment, |{right arrow over (R)}| is such that|{right arrow over (R)}|²=|{right arrow over (R)}|²+|{right arrow over(Q)}|².

In parallel, component 2240 normalizes the measured |{right arrow over(R)}| and |{right arrow over (Q)}| magnitudes. In an embodiment, |{rightarrow over (R)}| and |{right arrow over (Q)}| are normalized to generateIclk_phase and Qclk_phase signals such that|Iclk_phase|²+|Qclk_phase|²=constant, where |Iclk_phase| and|Qclk_phase| represent normalized magnitudes of |{right arrow over (I)}|and |{right arrow over (Q)}|. Typically, given that the constant has avalue A, the measured |{right arrow over (I)}| and |{right arrow over(I)}| magnitudes are both divided by the quantity

$\frac{A}{\sqrt{{\overset{->}{I}}^{2} + {\overset{->}{Q}}^{2}}}$

Component 2250 receives the calculated |{right arrow over (R)}|magnitude from component 2230, and based on it calculates a phase shiftangle φ between first and second constant envelope constituents. Usingthe calculated phase shift angle φ, component 2050 then calculatesin-phase and quadrature amplitude information associated with the firstand second constant envelope constituents.

In the embodiment of FIG. 22, the phase shift angle φ is illustrated asa function f(|{right arrow over (R)}|) of the calculated magnitude|{right arrow over (R)}|.

Referring to FIG. 22, components 2240 and 2250 output the normalized|Iclk_phase| and |Qclk_phase| magnitude information and the calculatedamplitude information to DAC's for input into the appropriate vectormodulators. In embodiments, the output values are separately output todigital-to-analog converters. As shown in the embodiment of FIG. 12, forexample, signals 1220, 1222, 1224, and 1226 are output separately toDACs 1230, 1232, 1234, and 1236, respectively. In other embodiments,signals 1220, 1222, 1224, and 1226 are output into a single DAC as shownin FIGS. 13 and 13A.

3.4.3) Direct Cartesian 2-Branch Transfer Function

FIG. 23 is a process flowchart 2300 that illustrates an example I and Qtransfer function embodiment according to the Direct Cartesian 2-BranchVPA embodiment. The process begins at step 2310, which includesreceiving in-phase (I) and quadrature (Q) data components of a basebandsignal. In the Direct Cartesian 2-Branch VPA embodiment of FIG. 17, forexample, this is illustrated by I and Q Data Transfer Function module1716 receiving I and Q information signal 1710.

Step 2320 includes determining the magnitudes |I| and |Q| of thereceived I and Q data components.

Step 2330 includes calculating a magnitude |R| of the baseband signalbased on the measured |I| and |Q| magnitudes. In an embodiment, |R| issuch that |R|²=|I|²+|Q|². In the embodiment of FIG. 17, for example,steps 2320 and 2330 are performed by I and Q Data Transfer Functionmodule 1716 based on received information signal 1710.

Step 2340 includes calculating a phase shift angle θ of the basebandsignal based on the measured |I| and |Q| magnitudes. In an embodiment, θis such that

${\theta = {\tan^{- 1}( \frac{Q}{I} )}},$

and wherein the sign of I and Q determine the quadrant of θ. In theembodiment of FIG. 17, for example, step 2340 is performed by I and QData Transfer Function module 1216 based on I and Q data componentsreceived in information signal 1210.

Step 2350 includes calculating in-phase and quadrature amplitudeinformation associated with a first and second constant envelopeconstituents of the baseband signal. In the embodiment of FIG. 17, forexample, step 2350 is performed by I and Q Data Transfer Function module1716 based on previously calculated magnitude |R| and phase shift angleθ.

Step 2360 includes outputting the calculated amplitude information toDAC's for input into the appropriate vector modulators. In theembodiment of FIG. 17, for example, I and Q Data Transfer Functionmodule 1716 output information signals 1720, 1722, 1724, and 1726 tovector modulators 1750 and 1752 through DACs 1730, 1732, 1734, and 1736.In other embodiments, signals 1720, 1722, 1724, and 1726 are output intoa single DAC as shown in FIGS. 18 and 18A.

FIG. 24 is a block diagram that illustrates an exemplary embodiment 2400of a transfer function module implementing the process flowchart 2300.In the example of FIG. 24, transfer function module 2400 (such astransfer function module 1716) receives I and Q data signal 2410, suchas signal 1710 in FIG. 17. In an embodiment, I and Q data signal 2410includes I and Q data components of a baseband signal.

In an embodiment, transfer function module 2400 samples I and Q datasignal 2410 according to a sampling clock 2412. Sampled I and Q datasignals are received by component 2420 of transfer function module 2200.Component 2420 measures the magnitudes |{right arrow over (I)}| and|{right arrow over (Q)}| of the sampled I and Q data signals.

Based on the measured |{right arrow over (R)}| and |{right arrow over(Q)}| magnitudes, component 2430 calculates the magnitude |{right arrowover (R)}|. In an embodiment, |{right arrow over (R)}| is such that|{right arrow over (R)}|²=|{right arrow over (I)}|²+|{right arrow over(Q)}|².

In parallel, component 2240 calculates the phase shift angle θ of thebaseband signal. In an embodiment, θ is such that

${\theta = {\tan^{- 1}( \frac{\overset{->}{Q}}{\overset{->}{I}} )}},$

where the sign of I and Q determine the quadrant of θ.

Component 2450 receives the calculated |{right arrow over (R)}|magnitude from component 2430, and based on it calculates a phase shiftangle φ between first and second constant envelope constituent signals.In the embodiment of FIG. 24, the phase shift angle φ is illustrated asa function f₃|{right arrow over (R)}|) of the calculated magnitude|{right arrow over (R)}|. This is further described in section 3.4.4.

In parallel, component 2450 receives the calculated phase shift angle θfrom component 2440. As functions of φ and θ, component 2450 thencalculates in-phase and quadrature amplitude information for the vectormodulator inputs that generate the first and second constant envelopeconstituents. In an embodiment, the in-phase and quadrature amplitudeinformation supplied to the vector modulators are according to theequations provided in (18).

Component 2450 outputs the calculated amplitude information tosubsequent stages of the vector power amplifier. In embodiments, theoutput values are separately output to digital-to-analog converters. Asshown in the embodiment of FIG. 17, for example, signals 1720, 1722,1724, and 1726 are output separately to DACs 1730, 1732, 1734, and 1736,respectively. In other embodiments, signals 1720, 1722, 1724, and 1726are output into a single DAC as shown in FIGS. 18 and 18A.

3.4.4) Magnitude to Phase Shift Transform

Embodiments of f(|I|), ƒ(|{right arrow over (Q)}|) of FIG. 20 and f(|R|)of FIGS. 22 and 24 shall now be further described.

According to the present invention, any periodic waveform that can berepresented by a Fourier series and a Fourier transform can bedecomposed into two or more constant envelope signals.

Below are provided two examples for sinusoidal and square waveforms.

3.4.4.1) Magnitude to Phase Shift Transform for Sinusoidal Signals:

Consider a time-varying complex envelope sinusoidal signal r(t). In thetime domain, it can be represented as:

r(t)=R(t)sin(ωt+δ(t))  (20)

where R(t) represents the signal's envelope magnitude at time t, δ(t)represents the signal's phase shift angle at time t, and ω representsthe signal's frequency in radians per second.

It can be verified that, at any time instant t, signal r(t) can beobtained by the sum of two appropriately phased equal and constant orsubstantially equal and constant envelope signals. In other words, itcan be shown that:

R(t)sin(ωt+δ(t))=A sin(ωt)+A sin(ωt+φ(t))  (21)

for an appropriately chosen phase shift angle φ(t) between the twoconstant envelope signals. The phase shift angle φ(t) will be derived asa function of R(t) in the description below. This is equivalent to themagnitude to phase shift transform for sinusoidal signals.

Using a sine trigonometric identity, equation (21) can be re-written as:

R(t)sin(ωt+δ(t))=A sin(ωt)+A sin(ωt)cos φ(t)+A sin(φ(t))cos ωt;

R(t)sin(ωt+δ(t))=A sin(φ(t))cos ωt+A(1+cos φ(t))sin φt.  (22)

Note, from equation (22), that signal r(t) is written as a sum of anin-phase component and a quadrature component. Accordingly, the envelopemagnitude R(t) can be written as:

R(t)=√{square root over ((A sin(φ(t)))²+(A(1+cos(φ(t))))²)}{square rootover ((A sin(φ(t)))²+(A(1+cos(φ(t))))²)};

R(t)=√{square root over (2A(A+cos(φ(t))).)}  (23)

Equation (23) relates the envelope magnitude R(t) of signal r(t) to thephase shift angle φ(t) between two constant envelope constituents ofsignal r(t). The constant envelope constituents have equal orsubstantially equal envelope magnitude A, which is typically normalizedto 1.

Inversely, from equation (23), the phase shift angle φ(t) can be writtenas a function of R(t) as follows:

$\begin{matrix}{{\varphi (t)} = {{\arccos( {\frac{{R(t)}^{2}}{2A^{2}} - 1} )}.}} & (24)\end{matrix}$

Equation (24) represents the magnitude to phase shift transform for thecase of sinusoidal signals, and is illustrated in FIG. 26.

3.4.4.2) Magnitude to Phase Shift Transform for Square Wave Signals:

FIG. 28 illustrates a combination of two constant envelope square wavesignals according to embodiments of the present invention. In FIG. 28,signals 2810 and 2820 are constant envelope signals having a period T, aduty cycle γT (0<γ<1), and envelope magnitudes A1 and A2, respectively.

Signal 2830 results from combining signals 2810 and 2820. According toembodiments of the present invention, signal 2830 will have a magnitudeequal or substantially equal to a product of signals 2810 and 2820. Inother words, signal 2830 will have a magnitude of zero whenever eitherof signals 2810 or 2820 has a magnitude of zero, and a non-zeromagnitude when both signals 2810 and 2820 have non-zero magnitudes.

Further, signal 2830 represents a pulse-width-modulated signal. In otherwords, the envelope magnitude of signal 2830 is determined according tothe pulse width of signal 2830 over one period of the signal. Morespecifically, the envelope magnitude of signal 2830 is equal orsubstantially to the area under the curve of signal 2830.

Referring to FIG. 28, signals 2810 and 2820 are shown time-shiftedrelative to each other by a time shift t′. Equivalently, signals 2810and 2820 are phase-shifted relative to each other by a phase shift angle

$\varphi = {( \frac{t^{\prime}}{T} ) \times 2\pi}$

radians.

Still referring to FIG. 28, note that the envelope magnitude R of signal2830, in FIG. 28, is given by:

R=A ₁ ×A ₂×(γT−t′)  (25)

Accordingly, it can be deduced that φ is related to R according to:

$\begin{matrix}{\varphi = {\lbrack {\gamma - \frac{R}{T( {A_{1}A_{2}} )}} \rbrack \times {( {2\pi} ).}}} & (26)\end{matrix}$

Note, from equation (26), that R is at a maximum of γA1A2 when φ=0. Inother words, the envelope magnitude is at a maximum when the twoconstant envelope signals are in-phase with each other.

In typical implementations, signals 2810 and 2820 are normalized andhave equal or substantially equal envelope magnitude of 1. Further,signals 2810 and 2820 typically have a duty cycle of 0.5. Accordingly,equation (26) reduces to:

$\begin{matrix}{\varphi = {\lbrack {0.5 - \frac{R}{T}} \rbrack \times {( {2\pi} ).}}} & (27)\end{matrix}$

Equation (27) illustrates the magnitude to phase shift transform for thecase of normalized and equal or substantially equal envelope magnitudesquare wave signals. Equation (27) is illustrated in FIG. 26.

3.4.5) Waveform Distortion Compensation

In certain embodiments, magnitude to phase shift transforms may not beimplemented exactly as theoretically or practically desired. In fact,several factors may exist that require adjustment or tuning of thederived magnitude to phase shift transform for optimal (or at leastimproved) operation. In practice, phase and amplitude errors may existin the vector modulation circuitry, gain and phase imbalances can occurin the vector power amplifier branches, and distortion may exist in theMISO amplifier itself including but not limited to errors introduced bydirectly combining at a single circuit node transistor outputs withinthe MISO amplifier described herein. Each of these factors eithersingularly or in combination will contribute to output waveformdistortions that result in deviations from the desired output signalr(t). When output waveform distortion exceeds system designrequirements, waveform distortion compensation may be required.

FIG. 25 illustrates the effect of waveform distortion on a signal usingphasor signal representation. In FIG. 25, {right arrow over (R)}represents a phasor representation of a desired signal r(t). In theexample of FIG. 25, waveform distortion can cause the actual outputphasor to vary from r(t) anywhere within the phasor error region. Anexemplary phasor error region is illustrated in FIG. 25, and is equal orsubstantially equal to the maximum error vector magnitude. Phasors{right arrow over (R₁)} and {right arrow over (R₂)} represent examplesof potential output phasors that deviate from the desired r(t).

According to embodiments of the present invention, waveform distortionscan be measured, calculated, or estimated during the manufacture of thesystem and/or in real time or non-real time operation. FIG. 54A and FIG.55 are examples of methods that can be used for phasor error measurementand correction. These waveform distortions can be compensated for orreduced at various points in the system. For example, a phase errorbetween the branch amplifiers can be adjusted by applying an analogvoltage offset to the vector modulation circuitry, within the transferfunction, and/or using real time or non-real time feedback techniques asshown in the example system illustrated in FIGS. 58, 59 and 60.Similarly, branch amplification imbalances can be adjusted by applyingan analog voltage offset to the vector modulation circuitry, within thetransfer function, and/or using real time or non-real time feedbacktechniques as shown in FIGS. 58, 59 and 60. In the system illustrated inFIGS. 58, 59 and 60, for example, waveform distortion adjustment isperformed, as illustrated in FIG. 60, using Differential BranchAmplitude Measurement Circuitry 6024 and Differential Branch PhaseMeasurement Circuitry 6026, which provide a Differential BranchAmplitude signal 5950 and a Differential Branch Phase signal 5948,respectively. These signals are input into an A/D Converter 5732 byinput signal selector 5946, with the values generated by A/D converter5732 being input into Digital Control Module 5602. Digital ControlModule 5602 uses the values generated by A/D converter 5732 to calculateadjusted or offset values to provide control voltages for phaseadjustments to Vector modulation circuitry 5922, 5924, 5926, and 5928and control voltages for amplitude adjustments to Gain Balance controlcircuitry 6016. In FIG. 58, these control voltages are illustrated usingGain Balance Control signal 5749 and Phase Balance Control signal 5751.The feedback approach described above also compensates for processvariations, temperature variations, IC package variations, and circuitboard variations by ensuring the system amplitude and phase errorsremain with a specified tolerance. Additional example feedback andfeedforward error measurement and compensation techniques are furtherdescribed in section 4.1.2.

In other embodiments, the measured, calculated, or estimated waveformdistortions are compensated for at the transfer function stage of thepower amplifier. In this approach, the transfer function is designed tofactor in and correct the measured, calculated, and/or estimatedwaveform distortions. FIG. 78 illustrates a mathematical derivation ofthe magnitude to phase shift transform in the presence of amplitude andphase errors in branches of the VPA. Equation (28) in FIG. 78 takes intoaccount both phase and amplitude errors in an exemplary embodiment. Notethat R*sin({acute over (ω)}*t+δ) in FIG. 78 can be representative ofeither {right arrow over (R₁)} or {right arrow over (R₂)} in FIG. 25,for example. Equation (28) assumes that amplitudes A1 and A2 of the VPAbranches can be different and that each branch can contain a respectivephase error φe1(t) and γe2(t). For reference purposes, in atheoretically perfect system, A1=A2 and φe1(t)=φe2(t)=0. δ(t) isadjusted by quadrant based on the sign value of the input vectors I(t)and Q(t). As such, with no amplitude or phase errors, the phasorcorresponding to R*sin({acute over (ω)}*t+δ) is aligned with the desiredphasor R in FIG. 25.

In some embodiments, in practice, amplitude and phase components of thephasor corresponding to R*sin({acute over (ω)}*t+δ) are compared to thedesired phasor {right arrow over (R)} to generate system amplitude andphase error deviations. These amplitude and phase error deviations fromthe desired phasor {right arrow over (R)}, as shown in FIG. 25, can beaccounted for in the system transfer function. In an embodiment, A1 andA2 can be substantially equalized and φe1(t) and γe2(t) can be minimizedby properly adjusting the control inputs to the vector modulationcircuitry. In an embodiment, as illustrated in FIG. 57, this isperformed by the digital control module, which provides, usingdigital-to-analog converters DAC_(—)01, DAC_(—)02, DAC_(—)03, andDAC_(—)04, control inputs to the vector modulation circuitry.

Accordingly, given the fact that equations such as equation (28) can beused to calculate the resultant phasor at any instant in time based onthe values of A1 and A2 and φe1(t) and φe2(t), transfer functionmodification(s) can be made to compensate for the system errors, andsuch transfer function modification(s) will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.Exemplary methods for generating error tables and/or mathematicalfunctions to compensate for system errors are described in Section4.1.2. It will be apparent to persons skilled in the relevant art(s)that these waveform distortion correction and compensation techniquescan be implemented in either the digital or the analog domains, andimplementation of such techniques will be apparent to persons skilled inthe relevant art(s) based on the teachings contained herein.

3.5) Output Stage

An aspect of embodiments of the present invention lies in summingconstituent signals at the output stage of a vector power amplifier(VPA). This is shown, for example, in FIG. 7 where the outputs of PAs770, 772, 774, and 776 are summed. This is similarly shown in FIGS. 8,12, 13, 17, and 18, for example. Various embodiments for combining theoutputs of VPAs are described herein. While the following is describedin the context of VPAs, it should be understood that the followingteachings generally apply to coupling or summing the outputs of anyactive devices in any application.

FIG. 29 illustrates a vector power amplifier output stage embodiment2900 according to an embodiment of the present invention. Output stage2900 includes a plurality of vector modulator signals 2910-{1, . . . ,n} being input into a plurality of corresponding power amplifiers (PAs)2920-{1, . . . , n}. As described above, signals 2910-{1, . . . , n}represent constituent signals of a desired output signal of the vectorpower amplifier.

In the example of FIG. 29, PAs 2910-{1, . . . , n} equally amplify orsubstantially equally amplify input signals 2910-{1, . . . , n} togenerate amplified output signals 2930-{1, . . . , n}. Amplified outputsignals 2930-{1, . . . , n} are coupled together directly at summingnode 2940. According to this example embodiment of the presentinvention, summing node 2940 includes no coupling or isolating element,such as a power combiner, for example. In the embodiment of FIG. 29,summing node 2940 is a zero-impedance (or near-zero impedance)conducting wire. Accordingly, unlike in conventional systems that employcombining elements, the combining of output signals according to thisembodiment of the present invention incurs minimal power loss.

In another aspect, output stage embodiments of the present invention canbe implemented using multiple-input single-output (MISO) poweramplifiers.

In another aspect, output stage embodiments of the present invention canbe controlled to increase the power efficiency of the amplifier bycontrolling the output stage current according to the desired outputpower level.

In what follows, various output stage embodiments according to VPAembodiments of the present invention are provided in section 3.5.1. Insection 3.5.2, embodiments of output stage current shaping functions,for increasing the power efficiency of certain VPA embodiments of thepresent invention, are presented. Section 3.5.3 describes embodiments ofoutput stage protection techniques that may be utilized for certainoutput stage embodiments of the present invention.

3.5.1) Output Stage Embodiments

FIG. 30 is a block diagram that illustrates a power amplifier (PA)output stage embodiment 3000 according to an embodiment of the presentinvention. Output stage embodiment 3000 includes a plurality of PAbranches 3005-{1, . . . , n}. Signals 3010-{1, . . . , n} incoming fromrespective vector modulators represent inputs for output stage 3000.According to this embodiment of the present invention, signals 3010-{1,. . . , n} represent equal and constant or substantially equal andconstant envelope constituent signals of a desired output signal of thepower amplifier.

PA branches 3005-{1, . . . , n} apply equal or substantially equal poweramplification to respective signals 3010-{1, . . . , n}. In anembodiment, the power amplification level through PA branches 3005-{1, .. . , n} is set according to a power level requirement of the desiredoutput signal.

In the embodiment of FIG. 30, PA branches 3005-{1, . . . , n} eachincludes a power amplifier 3040-{1, . . . , n}. In other embodiments,drivers 3030-{1, . . . , n} and pre-drivers 3020-{1, . . . , n}, asillustrated in FIG. 30, may also be added in a PA branch prior to thepower amplifier element. In embodiments, drivers and pre-drivers areemployed whenever a required output power level may not be achieved in asingle amplifying stage.

To generate the desired output signal, outputs of PA branches 3005-{1, .. . , n} are coupled directly at summing node 3050. Summing node 3050provides little or no isolation between the coupled outputs. Further,summing node 3050 represents a relatively lossless summing node.Accordingly, minimal power loss is incurred in summing the outputs ofPAs 3040-{1, . . . , n}.

Output signal 3060 represents the desired output signal of output stage3000. In the embodiment of FIG. 30, output signal 3060 is measuredacross a load impedance 3070.

FIG. 31 is a block diagram that illustrates another power amplifier (PA)output stage embodiment 3100 according to the present invention. Similarto the embodiment of FIG. 30, output stage 3100 includes a plurality ofPA branches 3105-{1, . . . , n}. Each of PA branches 3105-{1, . . . , n}may include multiple power amplification stages represented by apre-driver 3020-{1, . . . , n}, driver 3030-{1, . . . , n}, and poweramplifier 3040-{1, . . . , n}. Output stage embodiment 3100 furtherincludes pull-up impedances coupled at the output of each poweramplification stage to provide biasing of that stage. For example,pull-up impedances 3125-{1, . . . , n} and 3135-{1, . . . , n},respectively, couple the pre-driver and driver stage outputs to powersupply or independent bias power supplies. Similarly, pull-up impedance3145 couples the PA stage outputs to the power supply or an independentbias power supply. According to this embodiment of the presentinvention, pull-up impedances represent optional components that mayaffect the efficiency but not necessarily the operation of the outputstage embodiment.

FIG. 32 is a block diagram that illustrates another power amplifier (PA)output stage embodiment 3200 according to the present invention. Similarto the embodiment of FIG. 30, output stage 3200 includes a plurality ofPA branches 3205-{1, . . . , n}. Each of PA branches 3205-{1, . . . , n}may include multiple power amplification stages represented by apre-driver 3020-{1, . . . , n}, driver 3030-{1, . . . , n}, and poweramplifier 3040-{1, . . . , n}. Output stage embodiment 3200 alsoincludes pull-up impedances coupled at the output of each poweramplification stage to achieve a proper biasing of that stage. Further,output stage embodiment 3200 includes matching impedances coupled at theoutputs of each power amplification stage to maximize power transferfrom that stage. For example, matching impedances 3210-{1, . . . , n}and 3220-{1, . . . , n}, are respectively coupled to the pre-driver anddriver stage outputs. Similarly, matching impedance 3240 is coupled atthe PA stage output. Note that matching impedance 3240 is coupled to thePA output stage subsequent to summing node 3250.

In the above-described embodiments of FIGS. 30-32, the PA stage outputsare combined by direct coupling at a summing node. For example, in theembodiment of FIG. 30, outputs of PA branches 3005-{1, . . . , n} arecoupled together at summing node 3050. Summing node 3050 is a nearzero-impedance conducting wire that provides minimal isolation betweenthe coupled outputs. Similar output stage coupling is shown in FIGS. 31and 32. It is noted that in certain embodiments of the presentinvention, output coupling, as shown in the embodiments of FIGS. 30-32or embodiments subsequently described below, may utilize certain outputstage protection measures. These protection measures may be implementedat different stages of the PA branch. Further, the type of protectionmeasures needed may be PA implementation-specific. A further discussionof output stage protection according to an embodiment of the presentinvention is provided in section 3.5.3.

FIG. 33 is a block diagram that illustrates another power amplifier (PA)output stage embodiment 3300 according to the present invention. Similarto the embodiment of FIG. 30, output stage 3300 includes a plurality ofPA branches 3305-{1, . . . , n}. Each of PA branches 3305-{1, . . . , n}may include multiple power amplification stages represented by apre-driver 3020-{1, . . . , n}, driver 3030-{1, . . . , n}, and poweramplifier 3040-{1, . . . , n}. Output stage embodiment 3300 may alsoinclude pull-up impedances 3125-{1, . . . , n}, 3135-{1, . . . , n}, and3145 coupled at the output of each power amplification stage to achievea proper biasing of that stage. Additionally, output stage embodiment3300 may include matching impedances 3210-{1, . . . , n}, 3220-{1, . . ., n}, and 3240 coupled at the output of each power amplification stageto maximize power transfer from that stage. Further, output stageembodiment 3300 receives an autobias signal 3310, from an Autobiasmodule 3340, coupled at the PA stage input of each PA branch 3305-{1, .. . , n}. Autobias module 3340 controls the bias of PAs 3040-{1, . . . ,n}. In an embodiment, autobias signal 3340 controls the amount ofcurrent flow through the PA stage according to a desired output powerlevel and signal envelope of the output waveform. A further descriptionof the operation of autobias signal and the autobias module is providedbelow in section 3.5.2.

FIG. 34 is a block diagram that illustrates another power amplifier (PA)output stage embodiment 3400 according to the present invention. Similarto the embodiment of FIG. 30, output stage 3400 includes a plurality ofPA branches 3405-{1, . . . , n}. Each of PA branches 3405-{1, . . . , n}may include multiple power amplification stages represented by apre-driver 3020-{1, . . . , n}, driver 3030-{1, . . . , n}, and poweramplifier 3040-{1, . . . , n}. Output stage embodiment 3400 may alsoinclude pull-impedances 3125-{1, . . . , n}, 3135-{1, . . . , n}, and3145 coupled at the output of each power amplification stage to achievedesired biasing of that stage. Additionally, output stage embodiment3400 may include matching impedances 3210-{1, . . . , n}, 3220-{1, . . ., n}, and 3240 coupled at the output of each power amplification stageto maximize power transfer from that stage. Further, output stageembodiment 3400 includes a plurality of harmonic control circuitnetworks 3410-{1, . . . , n} coupled at the PA stage input of each PAbranch {1, . . . , n}. Harmonic control circuit networks 3410-{1, . . ., n} may include a plurality of resistance, capacitance, and/orinductive elements and/or active devices coupled in series or inparallel. According to an embodiment of the present invention, harmoniccontrol circuit networks 3410-{1, . . . , n} provide harmonic controlfunctions for controlling the output frequency spectrum of the poweramplifier. In an embodiment, harmonic control circuit networks 3410-{1,. . . , n} are selected such that energy transfer to the fundamentalharmonic in the summed output spectrum is increased while the harmoniccontent of the output waveform is decreased. A further description ofharmonic control according to embodiments of the present invention isprovided below in section 3.6.

FIG. 35 is a block diagram that illustrates another power amplifier (PA)output stage embodiment 3500 according to the present invention. Outputstage embodiment 3500 represents a differential output equivalent ofoutput stage embodiment 3200 of FIG. 32. In embodiment 3500, PA stageoutputs 3510-{1, . . . , n} are combined successively to result in twoaggregate signals. The two aggregate signals are then combined across aloading impedance, thereby having the output of the power amplifierrepresent the difference between the two aggregate signals. Referring toFIG. 35, aggregate signals 3510 and 3520 are coupled across loadingimpedance 3530. The output of the power amplifier is measured across theloading impedance 3530 as the voltage difference between nodes 3540 and3550. According to embodiment 3500, the maximum output of the poweramplifier is obtained when the two aggregate signals are 180 degreesout-of-phase relative to each other. Inversely, the minimum output powerresults when the two aggregate signals are in-phase relative to eachother.

FIG. 36 is a block diagram that illustrates another output stageembodiment 3600 according to the present invention. Similar to theembodiment of FIG. 30, output stage 3600 includes a plurality of PAbranches 3605-{1, . . . , n}. Each of PA branches {1, . . . , n} mayinclude multiple power amplification stages represented by a pre-driver3020-{1, . . . , n}, a driver 3030-{1, . . . , n}, and a power amplifier(PA) 3620-{1, . . . , n}.

According to embodiment 3600, PA's 3620-{1, . . . , n} include switchingpower amplifiers. In the example of FIG. 36, power amplifiers 3620-{1, .. . , n} include npn bipolar junction transistor (BJT) elements Q1, . .. , Qn. BJT elements Q1, . . . , Qn have common collector nodes.Referring to FIG. 36, collector terminals of BJT elements Q1, . . . , Qnare coupled together to provide summing node 3640. Emitter terminals ofBJT elements Q1, . . . , Qn are coupled to a ground node, while baseterminals of BJT elements Q1, . . . , Qn provide input terminals intothe PA stage.

FIG. 37 is an example (related to FIG. 36) that illustrates an outputsignal of the

PA stage of embodiment 3600 in response to square wave input signals.For ease of illustration, a two-branch PA stage is considered. In theexample of FIG. 37, square wave signals 3730 and 3740 are input,respectively, into BJT elements 3710 and 3720. Note than when either ofBJT elements 3710 or 3720 turns on, summing node 3750 is shorted toground. Accordingly, when either of input signals 3730 or 3740 is high,output signal 3780 will be zero. Further, output signal 3780 will behigh only when both input signals 3730 and 3740 are zero. According tothis arrangement, PA stage 3700 performs pulse-width modulation, wherebythe magnitude of the output signal is a function of the phase shiftangle between the input signals.

Embodiments are not limited to npn BJT implementations as describedherein. A person skilled in the art will appreciate, for example, thatembodiments of the present invention may be implemented using pnp BJTs,CMOS, NMOS, PMOS, or other type of transistors. Further, embodiments canbe implemented using GaAs and/or SiGe transistors with the desiredtransistor switching speed being a factor to consider.

Referring back to FIG. 36, it is noted that while PAs 3620-{1, . . . ,n) are each illustrated using a single BJT notation, each PA 3620-{1, .. . , n} may include a plurality of series-coupled transistors. Inembodiments, the number of transistors included within each PA is setaccording to a required maximum output power level of the poweramplifier. In other embodiments, the number of transistors in the PA issuch that the numbers of transistors in the pre-driver, driver, and PAstages conform to a geometric progression.

FIG. 38 illustrates an exemplary PA embodiment 3800 according to anembodiment of the present invention. PA embodiment 3800 includes a BJTelement 3870, a LC network 3860, and a bias impedance 3850. BJT element3870 includes a plurality of BJT transistors Q1, . . . , Q8 coupled inseries. As illustrated in FIG. 38, BJT transistors Q1, . . . , Q8 arecoupled together at their base, collector, and emitter terminals.Collector terminal 3880 of BJT element 3870 provides an output terminalfor PA 3800. Emitter terminal 3890 of BJT element 3870 may be coupled tosubstrate or to an emitter terminal of a preceding amplifier stage. Forexample, emitter terminal 3890 is coupled to an emitter terminal of apreceding driver stage.

Referring to FIG. 38, LC network 3860 is coupled between PA inputterminal 3810 and input terminal 3820 of BJT element 3870. LC network3860 includes a plurality of capacitive and inductive elements.Optionally, a Harmonic Control Circuit network 3830 is also coupled atinput terminal 3820 of BJT element 3870. As described above, the HCCnetwork 3830 provides a harmonic control function for controlling theoutput frequency spectrum of the power amplifier.

Still referring to FIG. 38, bias impedance 3850 couples Iref signal 3840to input terminal 3820 of BJT element 3870. Iref signal 3840 representsan autobias signal that controls the bias of BJT element 3870 accordingto a desired output power level and signal envelope characteristics.

It is noted that, in the embodiment of FIG. 38, BJT element 3870 isillustrated to include 8 transistors. It can be appreciated by a personskilled in the art, however, that BJT element 3870 may include anynumber of transistors as required to achieve the desired output powerlevel of the power amplifier.

In another aspect, output stage embodiments can be implemented usingmultiple-input single-output (MISO) power amplifiers. FIG. 51A is ablock diagram that illustrates an exemplary MISO output stage embodiment5100A. Output stage embodiment 5100A includes a plurality of vectormodulator signals 5110-{1, . . . , n} that are input into MISO poweramplifier (PA) 5120. As described above, signals 5110-{1, . . . , n}represent constant envelope constituents of output signal 5130 of thepower amplifier. MISO PA 5120 is a multiple input single output poweramplifier. MISO PA 5120 receives and amplifies signals 5110-{1, . . . ,n} providing a distributed multi signal amplification process togenerate output signal 5130.

It is noted that MISO implementations, similar to the one shown in FIG.51A, can be similarly extended to any of the output stage embodimentsdescribed above. More specifically, any of the output stage embodimentsof FIGS. 29-37 can be implemented using a MISO approach. Additional MISOembodiments will now be provided with reference to FIGS. 51B-I. It isnoted that any of the embodiments described above can be implementedusing any of the MISO embodiments that will now be provided.

Referring to FIG. 51A, MISO PA 5120 can have any number of inputs asrequired by the substantially constant envelope decomposition of thecomplex envelope input signal. For example, in a two-dimensionaldecomposition, a two-input power amplifier can be used. According toembodiments of the present invention, building blocks for creating MISOPAs for any number of inputs are provided. FIG. 51B illustrates severalMISO building blocks according to an embodiment of the presentinvention. MISO PA 5110B represents a two-input single-output PA block.In an embodiment, MISO PA 5110B includes two PA branches. The PAbranches of MISO PA 5110B may be equivalent to any PA branches describedabove with reference to FIGS. 29-37, for example. MISO PA 5120Brepresents a three-input single-output PA block. In an embodiment, MISOPA 5120B includes three PA branches. The PA branches of MISO PA 5120Bmay equivalent to any PA branches described above with reference toFIGS. 29-37, for example.

Still referring to FIG. 51B, MISO PAs 5110B and 5120B represent basicbuilding blocks for any multiple-input single-output power amplifieraccording to embodiments of the present invention. For example, MISO PA5130B is a four-input single-output PA, which can be created by couplingtogether the outputs of two two-input single-output PA blocks, such asMISO PA 5110B, for example. This is illustrated in FIG. 51C. Similarly,it can be verified that MISO PA 5140B, an n-input single-output PA, canbe created from the basic building blocks 5110B and 5120B.

FIG. 51D illustrates various embodiments of the two-input single outputPA building block according to embodiments of the present invention.

Embodiment 5110D represents an npn implementation of the two-inputsingle output PA building block. Embodiment 5110D includes two npntransistors coupled together using a common collector node, whichprovides the output of the PA. A pull-up impedance (not shown) can becoupled between the common collector node and a supply node (not shown).

Embodiment 5130D represents a pnp equivalent of embodiment 5110D.Embodiment 5130D includes two pnp transistors coupled at a commoncollector node, which provides the output of the PA. A pull-downimpedance (not shown) can be coupled between the common collector nodeand a ground node (not shown).

Embodiment 5140D represents a complementary npn/pnp implementation ofthe two-input single output PA building block. Embodiment 5140D includesan npn transistor and a pnp transistor coupled at a common collectornode, which provides the output of the PA.

Still referring to FIG. 51D, embodiment 5120D represents a NMOSimplementation of the two-input single output PA building block.Embodiment 5120D includes two NMOS transistors coupled at a common drainnode, which provides the output of the PA.

Embodiment 5160D represents an PMOS equivalent of embodiment 5120D.Embodiment 5120D includes two PMOS transistors coupled at a common drainnode, which provides the output of the PA.

Embodiment 5150D represents a complementary MOS implementation of thetwo-input single-output PA building block. Embodiment 5150D includes aPMOS transistor and an NMOS transistor coupled at common drain node,which provides the output of the PA.

Two-input single-output embodiments of FIG. 51D can be further extendedto create multiple-input single-output PA embodiments. FIG. 51Eillustrates various embodiments of multiple-input single-output PAsaccording to embodiments of the present invention.

Embodiment 5150E represents an npn implementation of a multiple-inputsingle-output PA. Embodiment 5150E includes a plurality of npntransistors coupled together using a common collector node, whichprovides the output of the PA. A pull-up impedance (not shown) can becoupled between the common collector node and a supply voltage (notshown). Note that an n-input single-output PA according to embodiment5150E can be obtained by coupling additional npn transistors to thetwo-input single-output PA building block embodiment 5110D.

Embodiment 5170E represents a pnp equivalent of embodiment 5150E.Embodiment 5170E includes a plurality of pnp transistors coupledtogether using a common collector node, which provides the output of thePA. A pull-down impedance (not shown) may be coupled between the commoncollector node and a ground node (not shown). Note than an n-inputsingle-output PA according to embodiment 5170E can be obtained bycoupling additional pnp transistors to the two-input single-output PAbuilding block embodiment 5130D.

Embodiments 5110E and 5130E represent complementary npn/pnpimplementations of a multiple-input single-output PA. Embodiments 5110Eand 5130E may include a plurality of npn and/or pnp transistors coupledtogether using a common collector node, which provides the output of thePA. Note that an n-input single-output PA according to embodiment 5110Ecan be obtained by coupling additional npn and/or pnp transistors to thetwo-input single-output PA building block embodiment 5140D. Similarly,an n-input single-output PA according to embodiment 5130E can beobtained by coupling additional npn and/or pnp transistors to thetwo-input single-output PA building block embodiment 5130D.

Embodiment 5180E represents an PMOS implementation of a multiple-inputsingle-output PA. Embodiment 5180E includes a plurality of PMOStransistors coupled together using a common drain node, which providesthe output of the PA. Note that an n-input single-output PA according toembodiment 5180E can be obtained by coupling additional NMOS transistorsto the two-input single-output PA building block embodiment 5160D.

Embodiment 5160E represents a NMOS implementation of multiple-inputsingle-output PA. Embodiment 5160E includes a plurality of NMOStransistors coupled together using a common drain node, which providesthe output of the PA. Note that an n-input single-output PA according toembodiment 5160E can be obtained by coupling additional PMOS transistorsto the two-input single-output PA building block embodiment 5120D.

Embodiments 5120E and 5140E complementary MOS implementations of amultiple-input single-output PA. Embodiments 5120E and 5140E include aplurality of npn and pnp transistors coupled together using a commondrain node, which provides the output of the PA. Note that a n-inputsingle-output PA according to embodiment 5120E can be obtained bycoupling additional NMOS and/or PMOS transistors to the two-inputsingle-output PA building block 5150D. Similarly, an n-inputsingle-output PA according to embodiment 5140E can be obtained bycoupling additional NMOS and/or PMOS transistors to the two-inputsingle-output PA building block 5160D.

FIG. 51F illustrates further multiple-input single-output PA embodimentsaccording to embodiments of the present invention. Embodiment 5110Frepresents a complementary npn/pnp implementation of a multiple-inputsingle-output PA. Embodiment 5110F can be obtained by iterativelycoupling together embodiments of PA building block 5140D. Similarly,embodiment 5120F represents an equivalent NMOS/PMOS complementaryimplementation of a multiple-input single-output PA. Embodiment 5120Fcan be obtained by iteratively coupling together embodiments of PAbuilding block 5150D.

It must be noted that the multiple-input single-output embodimentsdescribed above may each correspond to a single or multiple branches ofa PA. For example, referring to FIG. 29, any of the multiple-inputsingle-output embodiments may be used to replace a single or multiplePAs 2920-{1, . . . , n}. In other words, each of PAs 2920-{1, . . . , n}may be implemented using any of the multiple-input single-output PAembodiments described above or with a single-input single-output PA asshown in FIG. 29.

It is further noted that the transistors shown in the embodiments ofFIGS. 51D, 51E, and 51F may each be implemented using a series oftransistors as shown in the exemplary embodiment of FIG. 38, forexample.

FIG. 51G illustrates further embodiments of the multiple-inputsingle-output PA building blocks. Embodiment 5110G illustrates anembodiment of the two-input single-output PA building block. Embodiment5110G includes two PA branches that can each be implemented according tosingle-input single-output or multiple-input single-output PAembodiments as described above. Further, embodiment 5110G illustrates anoptional bias control signal 5112G that is coupled to the two branchesof the PA embodiment. Bias control signal 5112G is optionally employedin embodiment 5110G based on the specific implementation of the PAbranches. In certain implementations, bias control will be required forproper operation of the PA. In other implementations, bias control isnot required for proper operation of the PA, but may provide improved PApower efficiency, output circuit protection, or power on currentprotection.

Still referring to FIG. 51G, embodiment 5120G illustrates an embodimentof the three-input single-output PA building block. Embodiment 5120Gincludes three PA branches that can each be implemented according tosingle-input single-output or multiple-input single-output PAembodiments as described above. Further, embodiment 5120G illustrates anoptional bias control signal 5114G that is coupled to the branches ofthe PA embodiment. Bias control signal 5114G is optionally employed inembodiment 5120G based on the specific implementation of the PAbranches. In certain implementations, bias control will be required forproper operation of the PA. In other implementations, bias control isnot required for proper operation of the PA, but may provide improved PApower efficiency.

FIG. 51H illustrates a further exemplary embodiment 5100H of thetwo-input single-output PA building block. Embodiment 5100H includes twoPA branches that can each be implemented according to single-inputsingle-output or multiple-input single-output PA embodiments asdescribed above. Embodiment 5100H further includes optional elements,illustrated using dashed lines in FIG. 51H, that can be additionallyemployed in embodiments of embodiment 5100H. In an embodiment, PAbuilding block 5100H may include a driver stage and/or pre-driver stagein each of the PA branches as shown in FIG. 51H. Process detectors mayalso be optionally employed to detect process and temperature variationsin the driver and/or pre-driver stages of the PA. Further, optional biascontrol may be provided to each of the pre-driver, driver, and/or PAstages of each branch of the PA embodiment. Bias control may be providedto one or more the stages based on the specific implementation of thatstage. Further, bias control may be required for certainimplementations, while it can be optionally employed in others.

FIG. 51I illustrates a further exemplary embodiment 5100I of amultiple-input single-output PA. Embodiment 5100I includes at least twoPA branches that can each be implemented according to single-inputsingle-output or multiple-input single-output PA embodiments asdescribed above. Embodiment 5100I further includes optional elementsthat can be additionally employed in embodiments of embodiment 5100I. Inan embodiment, the PA may include driver and/or pre-driver stages ineach of the PA branches as shown in FIG. 51I. Process detectors may alsobe optionally employed to detect process and temperature variations inthe driver and/or pre-driver stages of the PA. Further, optional biascontrol may be provided to each of the pre-driver, driver, and/or PAstages of each branch of the PA embodiment. Bias control may be providedto one or more the stages based on the specific implementation of thatstage. Further, bias control may be required for certainimplementations, while it can be optionally employed in others.

3.5.2) Output Stage Current Control—Autobias Module

Embodiments of the output stage and optional pre-driver and driver stagebias and current control techniques according to embodiments of thepresent invention are described below. In certain embodiments, outputstage current control functions are employed to increase the outputstage efficiency of a vector power amplifier (VPA) embodiment In otherembodiments, output stage current control is used to provide outputstage protection from excessive voltages and currents which is furtherdescribe in section 3.5.3. In embodiments, output stage current controlfunctions are performed using the Autobias module described above withreference to FIG. 33. A description of the operation of the Autobiasmodule in performing these current control functions is also presentedbelow according to an embodiment of the present invention.

According to embodiments of the present invention, power efficiency ofthe output stage of a VPA can be increased by controlling the outputstage current of the VPA as a function of the output power and theenvelope of the output waveform.

FIG. 37, illustrates a partial schematic of a Multiple Input SingleOutput amplifier comprised of two NPN transistors with input signals S1and S2. When S1 and S2 are designed to be substantially similarwaveforms and substantially constant envelope signals, any time varyingcomplex-envelope output signal can be created at circuit node 3750 bychanging the phase relationship of S1 and S2.

FIG. 39 illustrates an example time varying complex-envelope outputsignal 3910 and its corresponding envelope signal 3920. Note than signal3910 undergoes a reversal of phase at an instant of time t₀.Correspondingly, envelope signal 3920 undergoes a zero crossing at timet₀. Output signal 3910 exemplifies output signals according to typicalwireless signaling schemes such as W-CDMA, QPSK, and OFDM, for example.

FIG. 40 illustrates example diagram FIG. 37's output stage current inresponse to output signal 3910. I_(out) signal 4010 represents outputstage current without autobias control, and I_(out) signal 4020represents output stage current with autobias control. Without autobiascontrol, as the phase shift between S1 and S2 changes from 0 to 180degrees, the output current I_(out) increases. With autobias control,the output current I_(out) decreases and can be minimized when at ornear t₀ of FIG. 39.

Note that I_(out) signal 4020 varies as a function of envelope signal3920. Accordingly, I_(out) signal 4020 is at the maximum when a maximumoutput power is required, but decreases as the required output powergoes down. Particularly, I_(out) signal 4020 approaches zero as theassociated output power goes to zero. Accordingly, a person skilled inthe art will appreciate that output stage current control, according toembodiments of the present invention, results in significant powersavings and increases the power efficiency of the power amplifier.

According to embodiments of the present invention, output stage currentcontrol may be implemented according to a variety of functions. In anembodiment, the output stage current can be shaped to correspond to thedesired output power of the amplifier. In such an embodiment, the outputstage current is a function that is derived from the envelope of thedesired output signal, and the power efficiency will increase.

FIG. 41 illustrates exemplary autobias output stage current controlfunctions 4110 and 4120 according to embodiments of the presentinvention. Function 4110 may represent a function of output power andsignal envelope as described above. On the other hand, function 4120 mayrepresent a simple shaping function that goes to a minimum value for apre-determined amount of time when the output power is below a thresholdvalue. Accordingly, functions 4110 and 4120 represent two cases ofautobias output stage current control functions with autobias controlsignal 4110 resulting in I_(out) response 4130 and autobias controlsignal 4120 resulting in I_(out) response 4140. The invention, however,is not limited to those two exemplary embodiments. According toembodiments of the present invention, output stage autobias currentcontrol functions may be designed and implemented to accommodate theefficiency and current consumption requirements of a particular vectorpower amplifier design.

In implementation, several approaches exist for performing output stagecurrent control. In some embodiments, output stage current shaping isperformed using the Autobias module. The Autobias module is illustratedas autobias circuitry 714 and 716 in the embodiments of FIGS. 7 and 8.Similarly, the Autobias module is illustrated as autobias circuitry 1218in the embodiments of FIGS. 12 and 13, and as autobias circuitry 1718 inthe embodiments of FIGS. 17 and 18.

Output stage current control using Autobias is depicted in processflowchart 4800 of the embodiment of FIG. 48. The process begins in step4810, which includes receiving output power and output signal envelopeinformation of a desired output signal of a vector power amplifier(VPA). In some embodiments, implementing output stage current controlusing Autobias requires a priori knowledge of the desired output powerof the amplifier. Output power information may be in the form ofenvelope and phase information. For example, in the embodiments of FIGS.7, 8, 12, 13, 17, and 18, output power information is included in I andQ data components received by the VPA embodiment. In other embodiments,output power information may be received or calculated using othermeans.

Step 4820 includes calculating a signal according to the output powerand output envelope signal information. In embodiments, an Autobiassignal is calculated as a function of some measure of the desired outputpower. For example, the Autobias signal may be calculated as a functionof the envelope magnitude of the desired output signal. Referring to theembodiments of FIGS. 7, 8, 12, 13, 17, and 18, for example, it is notedthat the Autobias signal (signals 715 and 717 in FIGS. 7 and 8, signal1228 in FIGS. 12 and 13, and signals 1728 in FIGS. 17 and 18) iscalculated according to received I and Q data components of a desiredoutput signal. In certain embodiments, such as the ones described inFIGS. 7, 8, 12, 13, 17, and 18, the Autobias signal is calculated by anAutobias module being provided output power information. In otherembodiments, the Autobias signal may be calculated by the I and Q DataTransfer Function module(s) of the VPA. In such embodiments, an Autobiasmodule may not be required in implementation. In embodiments, the I andQ Data Transfer Function module calculates a signal, outputs the signalto a DAC which output signal represents the Autobias signal.

Step 4830 includes applying the calculated signal at an output stage ofthe VPA, thereby controlling a current of the output stage according tothe output power of the desired output signal. In embodiments, step 4830includes coupling the Autobias signal at the PA stage input of the VPA.This is illustrated, for example, in the embodiments of FIGS. 33 and 42where Autobias signal 3310 is coupled at the PA stage input of the VPAembodiment. In these embodiments, Autobias signal 3310 controls the biasof the PA stage transistors according to the output power of the desiredoutput signal of the VPA embodiment. For example, Autobias signal 3310may cause the PA stage transistors to operate in cutoff state when thedesired output power is minimal or near zero, thereby drawing little orno output stage current. Similarly, when a maximum output power isdesired, Autobias signal 3310 may bias the PA stage transistors tooperate in class C, D, E, etc. switching mode. Autobias signal 3310 mayalso cause the PA stage transistors or FETs to operate in forward orreverse biased states according to the desired output power and signalenvelope characteristics.

In other embodiments, step 4830 includes coupling the Autobias signalusing pull-up impedances at the PA stage input and optionally the inputsof the driver and pre-driver stages of the VPA. FIGS. 38 and 43illustrate such embodiments. For example, in the embodiment of FIG. 38,bias impedance 3850 couples Autobias Iref signal 3840 to input terminal3820 of BJT element 3870. BJT element 3870 represents the PA stage ofone PA branch of an exemplary VPA embodiment. Similarly, in theembodiment of FIG. 43, Autobias signal 4310 is coupled to transistorsQ1, . . . , Q8 through corresponding bias impedances Z1, . . . , Z8.Transistors Q1, . . . , Q8 represent the PA stage of one branch of anexemplary VPA embodiment.

Embodiments for implementing the Autobias circuitry described above willnow be provided. FIG. 27 illustrates three embodiments 2700A, 2700B, and2700C for implementing the Autobias circuitry. These embodiments areprovided for illustrative purposes, and are not limiting. Otherembodiments will be apparent to persons skilled in the art(s) based onthe teachings contained herein.

In embodiment 2700A, Autobias circuitry 2700A includes an AutobiasTransfer Function module 2712, a DAC 2714, and an optional interpolationfilter 2718. Autobias circuitry 2700A receives an I and Q Data signal2710. Autobias Transfer Function module 2712 processes the received Iand Q Data signal 2710 to generate an appropriate bias signal 2713.Autobias Transfer Function module 2712 outputs bias signal 2713 to DAC2714. DAC 2714 is controlled by a DAC clock 2716 which may be generatedin Autobias transfer module 2712. DAC 2714 converts bias signal 2713into an analog signal, and outputs the analog signal to interpolationfilter 2718. Interpolation filter 2718, which also serves as ananti-aliasing filter, shapes the DAC's output to generate Autobiassignal 2720, illustrated as Bias A in embodiment 5112G. Autobias signal2720 may be used to bias the PA stage and/or the driver stage, and/orthe pre-driver stage of the amplifier. In an embodiment, Autobias signal2720 may have several other Autobias signals derived therefrom to biasdifferent stages within the PA stage. This can be done using additionalcircuitry not included in embodiment 2700A.

In contrast, embodiment 2700B illustrates an Autobias circuitryembodiment in which multiple Autobias signals are derived within theAutobias circuitry. As shown in embodiment 2700B, circuit networks 2722,2726, and 2730, illustrated as circuit networks A, B, and C inembodiment 2700B, are used to derive Autobias signals 2724 and 2728 fromAutobias signal 2720. Autobias signals 2720, 2724, and 2728 are used tobias different amplification stages.

Embodiment 2700C illustrates another Autobias circuitry embodiment inwhich multiple Autobias signals are generated independently within theAutobias Transfer Function module 2712. In embodiment 2700C, AutobiasTransfer Function module 2712 generates multiple bias signals accordingto the received I and Q Data signal 2710. The bias signals may or maynot be related. Autobias Transfer Function module 2712 outputs thegenerated bias signals to subsequent DACs 2732, 2734, and 2736. DACs2732, 2734, and 2736 are controlled by DAC clock signals 2733, 2735, and2737, respectively. DACs 2732, 2734, and 2736 convert the received biassignals into analog signals, and output the analog signals to optionalinterpolation filters 2742, 2744, and 2746. Interpolation filters 2742,2744, and 2746, which also serve as anti-aliasing filters, shape theDACs outputs to generate Autobias signals 2720, 2724, and 2728. Similarto embodiment 2700B, Autobias signals 2720, 2724, and 2728 are used tobias different amplification stages such as the pre-driver, driver, andPA.

As noted above, Autobias circuitry embodiments according to the presentinvention are not limited to the ones described in embodiments 2700A,2700B, and 2700C. A person skilled in the art will appreciate, forexample, that Autobias circuitry can be extended to generate any numberof bias control signals as required to control the bias of variousstages of amplification, and not just three as shown in embodiments5200B and 5200C, for example.

3.5.3) Output Stage Protection

As described above, output stage embodiments according to embodiments ofthe present invention are highly power efficient as a result of beingable to directly couple outputs at the PA stage using no combining orisolating elements. Certain output stage embodiments in certaincircumstances and/or applications, however, may require additionalspecial output stage protection measures in order to withstand suchdirect coupling approach. This may be the case for example for outputstage embodiments such as 5110D, 5120D, 5130D, 5160D, 5150E, 5160E,5170E, and 5180E illustrated in FIGS. 51D and 51E. Note that, generally,complementary output stage embodiments, such as embodiments 5140D,5150D, 5110E, 5120E, 5130E, and 5140E of FIGS. 51D and 51E, do notrequire (but may optionally use) the same output stage protectionmeasures as will be described herein in this section. Output stageprotection measures and embodiments to support such measures are nowprovided.

In one aspect, transistors of distinct branches of a PA stage shouldgenerally not simultaneously be in opposite states of operation forextended periods of time. Following a restart or power on with no inputsbeing supplied to the final PA stages, transients within the PA branchesmay cause this mode to occur resulting in the PA stage transistorspotentially damaging one another or circuit elements connected to theoutput. Accordingly, embodiments of the present invention furtherconstrain the Autobias module to limit the output current in the PAstage.

In another aspect, it may be desired to ensure that the Autobias modulelimits the output voltages below the breakdown voltage specification ofthe PA stage transistors. Accordingly, in embodiments of the presentinvention, such as the one illustrated in FIG. 42 for example, afeedback element 4210 is coupled between the common collector node ofthe PA stage and the Autobias module. Feedback element 4210 monitors thecollector to base voltage of the PA stage transistors, and may constrainthe Autobias signal as necessary to protect the transistors and/orcircuit elements.

A person skilled in the art will appreciate that other output stageprotection techniques may also be implemented. Furthermore, output stageprotection techniques may be implementation specific. For example,depending on the type of PA stage transistors (npn, pnp, NMOS, PMOS,npn/pnp, NMOS/PMOS), different protection functions may be required.

3.6) Harmonic Control

According to embodiments of the present invention, an underlyingprinciple for each branch PA is to maximize the transfer of power to afundamental harmonic of the output spectrum. Typically, each branch PAmay be multi-stage giving rise to a harmonically rich output spectrum.In one aspect, transfer of real power is maximized for the fundamentalharmonic. In another aspect, for non-fundamental harmonics, real powertransfer is minimized while imaginary power transfer may be tolerated.Harmonic control, according to embodiments of the present invention, maybe performed in a variety of ways.

In one embodiment, real power transfer onto the fundamental harmonic ismaximized by means of wave-shaping of the PA stage input signals. Inpractice, several factors play a role in determining the optimal waveshape that results in a maximum real power transfer onto the fundamentalharmonic. Embodiment 3400 of the present invention, described above,represents one embodiment that employs waveshaping of PA stage inputsignals. In embodiment 3400, a plurality of harmonic control circuitry(HCC) networks 3410-{1, . . . , n} are coupled at the PA stage input ofeach PA branch {1, . . . , n}. HCC networks 3410-{1, . . . , n} have theeffect of waveshaping the PA stage inputs, and are typically selected soas to maximize real power transfer to the fundamental harmonic of thesummed output spectrum. According to embodiments of the presentinvention, waveshaping can be used to generate variations ofharmonically diverse waveforms. In other embodiments, as can be apparentto a person skilled in the art, waveshaping can be performed at thepre-driver and/or the driver stage.

In another embodiment, harmonic control is achieved by means ofwaveshaping of the PA stage output. FIG. 43 illustrates an exemplary PAstage embodiment 4300 of the present invention. In embodiment 4300,Autobias signal 4310 is coupled to transistors Q1, . . . , Q8 throughcorresponding bias impedances Z1, . . . , Z8. Notice that whenimpedances Z1, . . . , Z8 have different values, transistors Q1, . . . ,Q8 have different bias points and can be turned on at different times.This approach of biasing transistors Q1, . . . , Q8 is referred to asstaggered bias. Note that using staggered bias, the PA output waveformcan be shaped in a variety of ways depending on the values assigned tobias impedances Z1, . . . , Z8.

Harmonic control using staggered bias is depicted in process flowchart4900 of the embodiment of FIG. 49. The process begins in step 4910,which includes coupling an input signal at first ports of a plurality oftransistors of a power amplifier (PA) switching stage. In the exampleembodiment of FIG. 43, for example, step 4910 corresponds to couplingPA_IN signal 4310 at base terminals of the plurality of transistors Q1,. . . , Q8.

Step 4920 includes coupling a plurality of impedances between the firstports of the plurality of transistors and a bias signal. In the exampleembodiment of FIG. 43, for example, step 4920 is achieved by couplingimpedances Z1, . . . , Z8 between base terminals of respectivetransistors Q1, . . . , Q8 and Iref signal. In an embodiment, values ofthe plurality of impedances are selected to cause a time-staggeredswitching of the input signal, thereby harmonically shaping an outputsignal of the PA stage. In embodiments, a multi-stage staggered outputmay be generated by selecting multiple distinct values of the pluralityof impedances. In other embodiments, switching is achieved by selectingthe plurality of impedances to have equal or substantially equal value.

FIG. 44 illustrates an exemplary wave-shaped PA output using a two-stagestaggered bias approach. In a two-stage staggered bias approach, a firstset of the PA transistors is first turned on before a second set isturned on. In other words, the bias impedances take two differentvalues. Waveform 4410 represents an input waveform into the PA stage.Waveform 4420 represents the wave-shaped PA output according to atwo-stage staggered bias. Notice that output waveform 4420 slopes twiceas it transitions from 1 to 0, which corresponds to the first and secondsets of transistors turning on successively.

According to embodiments of the present invention, a variety ofmulti-stage staggered bias approaches may be designed. Bias impedancevalues may be fixed or variable. Furthermore, bias impedance values maybe equal or substantially equal, distinct, or set according to a varietyof permutations. For example, referring to the example of FIG. 43, oneexemplary permutation might set Z1=Z2=Z3=Z4 and Z5=Z6=Z7=Z8 resulting ina two-stage staggered bias.

3.7) Power Control

Vector power amplification embodiments of the present inventionintrinsically provide a mechanism for performing output power control.

FIG. 45 illustrates one approach for performing power control accordingto an embodiment of the present invention. In FIG. 45, phasors {rightarrow over (U₁)} and {right arrow over (L₁)} represent upper and lowerconstituents of a first phasor {right arrow over (R₁)}. {right arrowover (U₁)} and {right arrow over (L₁)} are constant magnitude and aresymmetrically shifted in phase relative to {right arrow over (R₁)} by aphase shift angle φ/2. Phasors {right arrow over (U₂)} and {right arrowover (L₂)} represent upper and lower constituents of a second phasor{right arrow over (R₂)}. {right arrow over (U₂)} and {right arrow over(L₂)} are constant magnitude and are symmetrically shifted in phaserelative to {right arrow over (R₂)} by a phase shift angle

$\frac{\varphi}{2} + {\varphi_{off}.}$

It is noted, from FIG. 45, that {right arrow over (R₁)} and {right arrowover (R₂)} are in-phase relative to each other but only differ inmagnitude. Furthermore, {right arrow over (U₂)} and {right arrow over(L₂)} are equally or substantially equally phased shifted relative to{right arrow over (U₁)} and {right arrow over (L₁)}, respectively.Accordingly, it can be inferred that, according to the presentinvention, a signal's magnitude can be manipulated without varying itsphase shift angle by equally or substantially equally shiftingsymmetrically its constituent signals.

According to the above observation, output power control can beperformed by imposing constraints on the phase shift angle of theconstituent signals of a desired output signal. Referring to FIG. 45,for example, by constraining the range of values that phase shift angle

$\frac{\varphi}{2}$

can take, magnitude constraints can be imposed on phasor {right arrowover (R₁)}.

According to embodiments of the present invention, a maximum outputpower level can be achieved by imposing a minimum phase shift anglecondition. For example, referring to FIG. 45, by setting a conditionsuch that

${\frac{\varphi}{2} \geq \varphi_{ff}},$

the magnitude of phasor {right arrow over (R₁)} is constrained not toexceed a certain maximum level. Similarly, a maximum phase shift anglecondition imposes a minimum magnitude level requirement.

In another aspect of power control, output power resolution is definedin terms of a minimum power increment or decrement step size. Accordingto an embodiment of the present invention, output power resolution maybe implemented by defining a minimum phase shift angle step size.Accordingly, phase shift angle values are set according to a discretevalue range having a pre-determined step size. FIG. 46 illustrates anexemplary phase shift angle spectrum, whereby phase shift angle

$\frac{\varphi}{2}$

is set according to a pre-determined value range having a minimum stepφ_(step).

A person skilled in the art will appreciate that a variety of powercontrol schemes may be implemented in a fashion similar to thetechniques described above. In other words, various power controlalgorithms can be designed, according to the present invention, bysetting corresponding constraints on phase shift angle values. It isalso apparent, based on the description above of data transferfunctions, that power control schemes can be naturally incorporated intoa transfer function implementation.

3.8) Exemplary Vector Power Amplifier Embodiment

FIG. 47 illustrates an exemplary embodiment 4700 of a vector poweramplifier according to the present invention. Embodiment 4700 isimplemented according to the Direct Cartesian 2-Branch VPA method.

Referring to FIG. 47, signals 4710 and 4712 represent incoming signalsfrom a transfer function stage. The transfer function stage is not shownin FIG. 47. Block 4720 represents a quadrature generator which may beoptionally implemented according to an embodiment of the presentinvention. Quadrature generator 4720 generates clock signals 4730 and4732 to be used by vector modulators 4740 and 4742, respectively.Similarly, signals 4710 and 4712 are input into vector modulators 4740and 4742. As described above, vector modulators 4740 and 4742 generateconstant envelope constituents that are, subsequently, processed by a PAstage. In embodiment 4700, the PA stage is multi-stage, whereby each PAbranch includes a pre-driver stage 4750-4752, a driver stage 4760-4762,and a power amplifier stage 4770-4772.

Further illustrated in FIG. 47 are Autobias signals 4774 and 4776, andterminals 4780 and 4782 for coupling harmonic control circuitry andnetworks. Terminal node 4780 represents the output terminal of thevector power amplifier, and is obtained by direct coupling of the two PAbranches' outputs.

4. ADDITIONAL EXEMPLARY EMBODIMENTS AND IMPLEMENTATIONS 4.1) Overview

Exemplary VPA implementations according to embodiments of the presentinvention will be provided in this section. Advantages of these VPAimplementations will be appreciated by persons skilled in the art basedon the teachings herein. We briefly describe below some of theseadvantages before presenting in more detail the exemplary VPAimplementations.

4.1.1) Control of Output Power and Power Efficiency

The exemplary VPA implementations enable several layers of functionalityfor performing power control and/or for controlling power efficiencyusing circuitry within the VPA. FIG. 52 illustrates this functionalityat a high level using a MISO VPA embodiment 5200. MISO VPA embodiment5200 is a 2 input single output VPA with optional driver and pre-driverstages in each branch of the VPA. As in previously describedembodiments, the input bias voltage or current to each amplificationstage (e.g., pre-driver stage, driver stage, etc.) of the VPA iscontrolled using a bias signal (also referred to as Autobias in otherembodiments). In embodiment 5200, separate bias signals Bias C, Bias B,and Bias A are coupled to the pre-driver, driver, and PA stages,respectively, of the VPA. Additionally, VPA embodiment 5200 includespower supply signals (Pre-Driver VSUPPLY, Driver VSUPPLY, and OutputStage VSUPPLY) that are used to power respective stages of the VPA. Inembodiments, these power supply signals are generated using voltagecontrolled power supplies and can be further used to bias theirrespective amplifications stages, thereby providing additionalfunctionality for controlling the overall power efficiency of the VPAand for performing power control, as well as other functions of the VPA.For example, when controlled independently, the power supply signals andbias signals can be used to operate different amplification stages ofthe VPA at different power supply voltages and bias points, enabling awide output power dynamic range for the VPA. In embodiments the voltagecontrolled power supplies can be implemented as continuously variablesupplies such as voltage controlled switching supplies which providevariable voltage supplies to the appropriate amplification stage. Inother embodiments the voltage controlled power supply can be implementedby using switches to provide different power supply voltages. Forexample, a VPA output stage and/or optional driver stages and/oroptional pre-driver stages power supply could be switched between 3.3V,1.8V, and 0V depending on the desired operating parameters.

4.1.2) Error Compensation and/or Correction

The exemplary VPA implementations provide different approaches formonitoring and/or compensating for errors in the VPA. These errors maybe due, among other factors, to process and/or temperature variations inthe VPA, phase and amplitude errors in the vector modulation circuitry,gain and phase imbalances in branches of the VPA, and distortion in theMISO amplifier (see, for example, Section 3.4.5 above). In previouslydescribed VPA embodiments, part of this functionality was embodied inthe process detector circuitry (e.g., process detector 792 in FIG. 7A,process detector 1282 in FIG. 12, process detector 1772 in FIG. 17).These approaches can be classified as feedforward, feedback, and hybridfeedforward/feedback techniques, and can be implemented in a variety ofways as will be further discussed in the following sections thatdescribe the exemplary VPA implementations. A conceptual description ofthese error monitoring and compensation approaches will be now provided.

FIGS. 54A and 54B are block diagrams that illustrate at a high levelfeedforward techniques for compensating for errors in a VPA. Feedforwardtechniques rely on a priori knowledge of expected errors in the VPA inorder to pre-compensate for these errors within the VPA. Thus,feedforward techniques include an error measurement phase (typicallyperformed in a test and characterization process) and a pre-compensationphase using the error measurements.

FIG. 54A illustrates a process 5400A for generating an error table orfunction that describes expected errors in I data and Q data at theoutput of the VPA (error measurement phase). Such errors are typicallydue to imperfections in the VPA. Process 5400A is typically performed ina testing lab prior to finalizing the VPA design, and includes measuringat the output of a receiver I and Q values that correspond to a range ofI and Q values at the input of the VPA. Typically, the input I and Qvalues are selected to generate a representative range of the 360°degrees polar space (for example, the I and Q values may be selected ata uniform spacing of 30° degrees). Subsequently, error differencesbetween the input I and Q values and the output I and Q values arecalculated. For example, after measuring I and Q at the output of thereceiver for a particular set of I and Q input values, a comparecircuitry calculates as I_(error) and Q_(error) the differences in Idata and Q data between the input I and Q values and the receiver outputI and Q values. I_(error) and Q_(error) represent the expected errors inI and Q at the output of the VPA for the particular set of I and Q inputvalues.

In an embodiment, the receiver is integrated with the VPA, or isprovided by an external calibration and/or testing device.Alternatively, the receiver is the receiver module in the deviceemploying the VPA (e.g., the receiver in a cellular phone). In thisalternative embodiment, the VPA error table and/or feedback informationcan be generated by this receiver module in the device.

The calculated I_(error) and Q_(error) values are used to generate anerror table or function representative of expected I and Q errors forvarious I and Q input values. In embodiments, the calculated I_(error)and Q_(error) values are further interpolated to generate error valuesfor an augmented range of I and Q input values, based on which the errortable or function is generated.

FIG. 54B illustrates feedforward error pre-compensation(pre-compensation phase) according to an embodiment of the presentinvention. As illustrated, I and Q input values are corrected for anyexpected I_(error) and Q_(error) values as determined by an error tableor function, prior to amplification by the VPA. I and Q errorpre-compensation may be performed at different stages and/or atdifferent temperatures and/or at different operating parameters withinthe VPA. In the embodiment of FIG. 54B, error correction occurs prior tothe amplification stage of the VPA. For example, I and Q errorcorrection may be performed by the transfer function module of the VPA,such as transfer function modules 1216 and 1726 of FIGS. 12 and 17, forexample. Several methods exist for implementing I and Q error correctionin the transfer function module of the VPA including using look uptables and/or digital logic to implement an error function. Typically,feedforward techniques require data storage such as RAM or NVRAM, forexample, to store data generated in the measurement phase.

In contrast to feedforward techniques, feedback techniques do notpre-compensate for errors but perform real-time measurements inside orat the output of the VPA to detect any errors or deviations due toprocess or temperature variations, for example. FIG. 55 is a blockdiagram that conceptually illustrates an exemplary Cartesian feedbackerror correction technique according to embodiments of the presentinvention. As will be further described below, FIG. 55 illustrates areceiver-based feedback technique, in which the output of the VPA isreceived by a receiver, before being fed back to the VPA. Other feedbacktechniques according to embodiments of the present invention will befurther described below. Feedback techniques may require additionalcircuitry to perform these real-time measurements, which may be made atdifferent stages within the VPA, but require minimal or no data storage.Several implementations exist for feedback error correction as will befurther described in the description of the exemplary VPAimplementations below.

Hybrid feedforward/feedback techniques include both feedforward andfeedback error pre-compensation and/or correction components. Forexample, a hybrid feedforward/feedback technique may pre-compensate forerrors but may also use low rate periodical feedback mechanisms tosupplement feedforward pre-compensation.

4.1.3) Multi-Band Multi-Mode VPA Operation

The exemplary VPA implementations provide several VPA architectures forconcurrently supporting multiple frequency bands (e.g., quad band)and/or multiple technology modes (e.g., tri mode) for data transmission.Advantages of these VPA architectures will be appreciated by a personskilled in the art based on the teachings to be provided herein. Inembodiments, the VPA architectures allow for using a single PA branchfor supporting both TDD (Time Division Duplex) and FDD (FrequencyDivision Duplex) based standards. In other embodiments, the VPAarchitectures allow for the elimination of costly and power inefficientcomponents at the output stage (e.g., isolators), typically required forFDD based standards. For the purpose of illustration and not limitation,frequency band allocation on lower and upper spectrum bands for variouscommunication standards is provided in FIG. 53. Note that the DCS 1800(Digital Cellular System 1800) and the PCS 1900 (Personal CommunicationsService 1900) bands can support different GSM-based implementations,also known as GSM-1800 and GSM-1900. The 3G TDD bands are allocated forthird generation time division duplex standards such as UMTS TDD(Universal Mobile Telephone System) and TD-SCDMA (TimeDivision-Synchronous Code Division Multiple Access), for example. The 3GFDD bands are allocated for third generation frequency division duplexstandards such as WCDMA (Wideband CDMA), for example.

As will be appreciated by persons skilled in the art based on theteachings herein, advantages enabled by the exemplary VPAimplementations exist in various aspects in addition to those describedabove. In the following, a more detailed description of the exemplaryVPA implementations will be provided. This includes a description ofdifferent implementations of the digital control circuitry of the VPAfollowed by a description of different implementations of the analogcore of the VPA. Embodiments of the present invention are not limited tothe specific implementations described herein. As will be understood bypersons skilled in the art based on the teachings herein, several otherVPA implementations may be obtained by combining features provided inthe exemplary VPA implementations. Accordingly, the exemplary VPAimplementations described below do not represent an exhaustive listingof VPA implementations according to embodiments of the presentinvention, and other implementations based on teachings contained hereinare also within the scope of the present invention. For example, certaindigital control circuitry could be integrated or combined with abaseband processor. In addition, certain analog control circuitry suchas quadrature generators and vector modulators can be implemented usingdigital control circuitry. In an embodiment, the VPA system can beimplemented in its entirety using digital circuitry and can beintegrated completely with a baseband processor.

4.2) Digital Control Module

The digital control module of the VPA includes digital circuitry that isused, among other functions, for signal generation, performancemonitoring, and VPA operation control. In Section 3, the signalgeneration functions of the digital control module (i.e., generatingconstant envelope signals) were described in detail with reference tothe transfer function module (state machine) of the digital controlmodule, in embodiments 700, 1200, and 1700, for example. The performancemonitoring functions of the digital control module include functions formonitoring and correcting for errors in the operation of the VPA and/orfunctions for controlling the bias of different stages of the VPA. TheVPA operation control functions of the digital control module include avariety of control functions related to the operation of the VPA (e.g.,powering up or programming VPA modules). In certain embodiments, thesecontrol functions may be optional. In other embodiments, these controlfunctions are accessible through the digital control module to externalprocessors connected to the VPA. In other embodiments, these functionsare integrated with baseband processors or other digital circuitry.Other functions are also performed by the digital control module inaddition to those described above. Digital control module functions andimplementations will now be provided in further detail.

FIG. 56 is a high level illustration of a digital control moduleembodiment 5600 according to an embodiment of the present invention.Digital control module embodiment 5600 includes an input interface 5602,an output interface 5604, a state machine 5606, a RAM (Random AccessMemory) 5608, and a NVRAM (Non-Volatile RAM) 5610. In embodiments, Ram5608, and/or NVRAM 5610 may be optional.

Input interface 5602 provides a plurality of buses and/or ports forinputting signals into digital control module 5600. These buses and/orports include, for example, buses and/or ports for inputting I and Qdata signals, control signals provided by an external processor, and/orclock signals. In an embodiment, input interface 5602 includes an I/Obus. In another embodiment, input interface 5602 includes a data bus forreceiving feedback signals from the analog core of the VPA. In anotherembodiment, input interface 5602 includes ports for reading values outof digital control module 5600. In an embodiment, values are read out ofdigital control module 5600 by an external processor (e.g., a basebandprocessor) connected to digital control module 5600.

Output interface 5604 provides a plurality of output buses and/or portsfor outputting signals from digital control module 5600. These outputbuses and/or ports include, for example, buses and/or ports foroutputting amplitude information signals (used to generate constantenvelope signals), bias control signals (Autobias signals), voltagecontrol signals (power supply signals), and output select signals.

State machine 5606 performs various functions related to the signalgeneration and/or performance monitoring functions of digital controlmodule 5600. In an embodiment, state machine 5606 includes a transferfunction module, as described in Section 3, for performing signalgeneration functions. In another embodiment, state machine 5606 includesmodules for generating, among other types of signals, bias controlsignals, power control signals, gain control signals, and phase controlsignals. In another embodiment, state machine 5606 includes modules forperforming error pre-compensation in a feedforward error correctionsystem.

RAM 5608 and/or NVRAM 5610 are optional components of digital controlmodule 5600. In embodiments, RAM 5608 and NVRAM 5610 reside externallyof digital control module 5600 and may be accessible to digital controlmodule 5600 through data buses connected to digital control module 5600via input interface 5602, for example. RAM 5608 and/or NVRAM 5610 may ormay not be needed depending on the specific VPA implementation. Forexample, a VPA implementation employing feedforward techniques for errorpre-compensation may require RAM 5608 or NVRAM 5610 to store errortables or functions. On the other hand, a feedback technique for errorcorrection may solely rely on digital logic modules in the state machineand may not require RAM 5608 or NVRAM 5610 storage. Similarly, theamount of RAM 5608 and NVRAM 5610 storage may depend on the specific VPAimplementation. Typically, when used, NVRAM 5610 is used for storingdata that is not generated in real time and/or that must be retainedwhen power is turned off. This includes, for example, error tablesand/or error values such as scalar values and angular values generatedin the testing and characterization phase of the VPA system and/or lookup tables used by transfer functions modules.

FIG. 57 illustrates an exemplary digital control module implementation5700 according to an embodiment of the present invention. Digitalcontrol module implementation 5700 illustrates in particular anexemplary input interface 5602 and an exemplary output interface 5604 ofan exemplary VPA digital control module 5700. As will be furtherdescribed below, signals of the input and output interfaces 5602 and5604 of VPA digital control module 5700 correlate directly with signalsfrom the analog core of the VPA and/or signals to/from one or moreexternal processors/controllers connected to the VPA. In the exampleembodiments described in the sections above, the analog core of the VPAwas represented by analog circuitry 186 together with PA stage 190-{1, .. . , n} in FIG. 1E, for example. It is noted that bit widths of databuses and/or signals of the input and output interfaces in FIG. 57 areprovided for the purpose of illustration only and are not limiting.

The input interface 5602 of exemplary digital control module 5700includes an A/D IN bus 5702, a digital I/O bus 5704, and a plurality ofcontrol signals 5706-5730. In other digital control moduleimplementations, the input interface 5602 may include more or less databuses, programming buses, and/or control signals.

A/D IN bus 5702 carries feedback information from the analog core of theVPA to the digital control module 5700. Feedback information can beused, among other functions, to monitor the output power of the VPAand/or for amplitude and/or phase variations in branches of the VPA. Asillustrated in FIG. 57, an A/D converter 5732 converts from analog todigital feedback information received from the analog core of the VPA(using A/D IN signal 5736) before sending it on A/D IN bus 5702 to thedigital control module 5700. In an embodiment, the digital controlmodule 5700 controls a clock signal A/D CLK 5734 of the A/D converter5732. In another embodiment, the digital control module 5700 controls aninput selector to the A/D converter 5732 to select between multiplefeedback signals at the input of the A/D converter 5732. In anembodiment, this is performed using A/D Input Selector signals5738-5746.

Digital I/O bus 5704 carries data and control signals into and out ofthe digital control module 5700 from and to one or more processors orcontrollers that may be connected to the VPA. In an embodiment, some ofcontrol signals 5706-5730 are used to inform the digital control module5700 of the type of information to expect on (or that is present on)digital I/O bus 5704. For example, PC/(I/Q)n signal 5724 indicates tothe digital control module 5700 whether power control information or I/Qdata is being sent over digital I/O bus 5704. Similarly, I/Qn signal5720 indicates to the digital control module 5700 whether I or Q data isbeing sent over digital I/O bus 5704.

Other control signals of the input interface 5602 of the VPA digitalcontrol module 5700 include Digital Enable/Disablen 5706, PRGM/RUNn5708, READ/WRITEn 5710, CLK OUT 5712, CLK_IN×2 Enable/Disablen 5714,CLK_IN×4 Enable/Disablen 5716, CLK_IN 5718, TX/RXn 5726, SYNTHPRGM/SYNTH RUNn 5728, and OUTPUT SEL/LATCHn 5730.

Digital Enable/Disablen signal 5706 controls the power-up, reset, andshut down of the VPA. Signals to power-up, reset, or shut down the VPAtypically come from a processor connected to the VPA. For example, whenused in a cellular phone, a baseband processor or controller of thecellular phone may shut down the VPA in receive mode and enable it intransmit mode.

PRGM/RUNn signal 5708 indicates to the digital control module 5700whether it is in programming or in run mode. In programming mode, thedigital control module 5700 can be programmed to enable the desiredoperation of the VPA. For example, memory (RAM 5608, NVRAM 5610) bits ofthe digital control module 5700 can be programmed to indicate thestandard to be used (e.g., WCDMA, EDGE, GSM, etc.) for communication.Programming of digital control module 5700 is done using digital I/O bus5704.

In an embodiment, the VPA is programmed and/or re-programmed (partiallyor completely) after it is installed in (or integrated with) the finalproduct or device employing the VPA. For example, when used in acellular phone, the VPA can be programmed after the cellular phone ismanufactured to provide the cellular phone with new, additional,modified or different features, such as features related to (1)supported waveforms, (2) power control, (3) enhanced efficiency, and/or(4) power-up and power-down profiles. The VPA can also be programmed toremove waveforms or other features as desired by the network provider.

Programming of the VPA may be payment based. For example, the VPA may beprogrammed to include features and enhancements selected and purchasedby the end-user.

In an embodiment, the VPA is programmed after the device is manufacturedusing any well known method or technique, including but not limited to:(1) programming the VPA using the programming interface of the deviceemploying the VPA; (2) programming the VPA by storing programming dataon a memory card readable by the device (a SIM card, for example, in thecase of a cellular phone); and/or (3) programming the VPA bytransferring programming data to the VPA wirelessly by the networkprovider or other source.

READ/WRITEn signal 5710 indicates to the digital control module 5700whether data is to be read from or written to the digital control modulestorage (RAM 5608 or NVRAM 5610) via digital I/O bus 5704. When data isbeing read out of the digital control module 5700, CLK OUT signal 5712indicates timing information for reading from digital I/O bus 5704.

CLK_IN signal 5718 provides a reference clock signal to the digitalcontrol module 5700. Typically, the reference clock signal is selectedaccording to the communication standards supported by the VPA. Forexample, in a dual-mode WCDMA/GSM system, it is desirable that thereference clock signal be a multiple of the WCDMA chip rate (3.84 MHz)and the GSM channel raster (200 KHz), with 19.2 MHz being a popular rateas the least common multiple of both. Further, CLK_IN signal 5718 can bemade a multiple of the reference clock signal. In an embodiment,CLK_IN×2 Enable/Disablen 5714, CLK_IN×4 Enable/Disablen 5716 can be usedto indicate to the VPA digital control module 5700 that a multiple ofthe reference clock is being provided.

TX/RXn signal 5726 indicates to the digital control module 5700 when thesystem (e.g., cellular phone) employing the VPA is going into transmitor receive mode. In an embodiment, the digital control module 5700 isnotified a short amount of time prior to the system going into transmitmode in order for it to power up the VPA. In another embodiment, thedigital control module 5700 is notified when the system is going intoreceive mode in order for it to enter a sleep mode or to shutdown theVPA.

SYNTH PRGM/SYNTH RUNn signal 5728 is used to program the synthesizerthat provides the reference frequency to the VPA (such as synthesizers5918 and 5920 shown in FIG. 59). When SYNTH PRGM 5728 is high, the VPAdigital control module 5700 can expect to receive data for programmingthe synthesizer on digital I/O bus 5704. Typically, programming of thesynthesizer is needed when selecting the VPA transmission frequency.When SYNTH RUN 5728 goes high, the synthesizer is instructed to run. Thesynthesizer may be integrated with the VPA system or provided as anexternal component or subsystem.

OUTPUT SEL/LATCHn signal 5730 is used to select the VPA output to beused for transmission. This may or may not be needed depending on thenumber of outputs of the VPA. When OUTPUT SEL 5730 goes high, thedigital control module 5700 expects to receive data for selecting theoutput on digital I/O bus 5704. When LATCH 5730 goes high, the digitalcontrol module 5700 ensures that the VPA output used for transmission isheld (cannot be changed) for the duration of the current transmitsequence.

The output interface 5604 of exemplary digital control module 5700includes a plurality of data buses (5748, 5750, 5752, 5754, 5756, 5758,5760, 5762, 5764, and 5766), a programming bus 5799, and a plurality ofcontrol signals (5768, 5770, 5772, 5744, 5776, 5778, 5780, 5782, 5784,5786, 5788, 5790, 5792, 5794, 5796, and 5798). In other embodiments ofdigital control module 5700, the output interface 5604 may have more orless data buses, programming buses, and/or control signals.

Data buses 5752, 5754, 5756, and 5758 carry digital information from thedigital control module 5700 that is used to generate the substantiallyconstant envelope signals in the analog core of the VPA. Note thatexemplary digital control module 5700 may be used in a 4-Branch VPAembodiment (see Section 3.1) or a 2-Branch VPA embodiment (see Section3.3). For example, digital information carried by data buses 5752, 5754,5756, and 5758 correspond to signals 722, 724, 726, and 728 in theembodiment of FIG. 7A or signals 1720, 1722, 1724, and 1726 in theembodiment of FIG. 17, and may be generated by the digital controlmodule 5700 according to equations (5) (for a 4-Branch VPA embodiment)and (18) (for a 2-Branch VPA embodiment). Digital information carried bydata buses 5752, 5754, 5756, and 5758 is converted from digital toanalog using respective Digital-to-Analog Converters (DACs 01-04) togenerate analog signals 5753, 5755, 5757, and 5759, respectively. Analogsignals 5753, 5755, 5757, and 5759 are input into vector modulators inthe analog core of the VPA as will be further described below withreference to the VPA analog core implementations. In an embodiment, DACs01-04 are controlled and synchronized by a Vector MOD DAC CLK signal5770 provided by the digital control module. Further, DACs 01-04 areprovided the same central reference voltage VREF_D signal 5743.

Data buses 5760 and 5762 carry digital information from the digitalcontrol module 5700 that is used to generate bias voltage signals forthe PA amplification stage and the driver amplification stage of the VPA(see FIG. 52 for illustration of different amplification stages of theVPA). In another embodiments additional control functions such aspre-driver Stage Bias Control is used. Digital information carried bydata bus 5760 is converted from digital to analog using DAC_(—)05 togenerate output stage bias signal 5761. Similarly, digital informationcarried by data bus 5762 is converted from digital to analog usingDAC_(—)06 to generate driver stage bias signal 5763. Output stage biassignal 5761 and driver stage bias signal 5763 correspond, for example,to bias signals A and B illustrated in embodiment 5100H. In anembodiment, DACs 05 and 06 are controlled and synchronized using anAutobias DAC CLK signal 5772, and are provided the same centralreference voltage VREF_E signal 5745.

Data buses 5764 and 5766 carry digital information from the digitalcontrol module 5700 that is used to generate voltage control signals forthe output stage and the driver stage of the VPA. Digital informationcarried by data bus 5764 is converted from digital to analog usingDAC_(—)07 to generate output stage voltage control signal 5765.Similarly, digital information carried by data bus 5766 is convertedfrom digital to analog using DAC_(—)08 to generate driver stage voltagecontrol signal 5767. Output stage voltage control signal 5765 and driverstage voltage control 5767 are used to generate supply voltages for theoutput stage and the driver stage, providing a further method forcontrolling the voltage of the output stage and driver stage of the VPA.In an embodiment, DACs 07 and 08 are controlled and synchronized using aVoltage Control DAC CLK signal 5774, and are provided the same centralreference voltage VREF_F signal 5747.

Data buses 5748 and 5750 carry digital information from the digitalcontrol module 5700 that is used to generate gain and phase balancecontrol signals. In an embodiment, the gain and phase balance controlsignals are generated in response to feedback gain and phase informationreceived from the analog core of the VPA on A/D IN bus 5702. Digitalinformation carried by data bus 5748 is converted from digital to analogusing DAC_(—)09 to generate analog gain balance control signal 5749.Similarly, digital information carried by data bus 5750 is convertedfrom digital to analog using DAC_(—)10 to generate analog phase balancecontrol 5751. Gain and phase balance control signals 5749 and 5751provide one mechanism for regulating gain and phase in the analog coreof the VPA. In an embodiment, DACs 09 and 10 are controlled andsynchronized using a Balance DAC CLK signal 5768, and are provided thesame central reference voltage VREF_B 5739.

Programming bus 5799 carries digital instructions from the digitalcontrol module 5700 that are used to program frequency synthesizer orsynthesizers in the analog core of the VPA. In an embodiment, digitalinstructions carried by programming bus 5799 are generated according todata received on digital I/O bus 5704, when SYNTH PRGM signal 5728 ishigh. Digital instructions for programming the frequency synthesizersinclude instructions for setting the appropriate synthesizer (HI Band orLow Band) to generate a frequency according to the selectedcommunication standard. In an embodiment, programming bus 5799 is a3-wire programming bus.

In addition to the data and programming buses described above, theoutput interface 5604 includes a plurality of control signals.

In conjunction with programming bus 5799, used for programming thefrequency synthesizers of the analog VPA core, HI Band Enable/Disablenand Low Band Enable/Disablen control signals 5796 and 5798 are generatedto control which of a high band frequency synthesizer and a low bandfrequency synthesizer of the analog VPA core is enabled/disabled.

Control signals 5738, 5740, 5742, 5744, and 5746 control an inputselector for multiplexing feedback signals from the analog core of theVPA onto A/D IN input signal 5736 of A/D converter 5732. In anembodiment, control signals 5738, 5740, 5744, and 5746 control themultiplexing of a power output feedback signal, a differential branchamplitude feedback signal, and a differential branch phase feedbacksignal on A/D IN signal 5736. Other feedback signals may be available inother embodiments. In an embodiment, the feedback signals aremultiplexed according to a pre-determined multiplexing cycle. In anotherembodiment, certain feedback signals are periodically carried by A/D INsignal 5736, while others are requested on-demand by the digital controlmodule.

Output select control signals 5776, 5778, 5780, 5782, and 5784 aregenerated by the digital control module 5700 in order to select a VPAoutput, when the particular VPA implementation supports a plurality ofoutputs for different frequency bands and/or technology modes. In anembodiment, output select control signals 5776, 5778, 5780, 5782, and5782 are generated according to digital control module input signal5730. In the example implementation of FIG. 57, the digital controlmodule 5700 provides five output select control signals for selectingone of five different VPA outputs. In an embodiment, output selectcontrol signals 5776, 5778, 5780, 5782, and 5784 control circuitrywithin the analog core of the VPA in order to power up circuitrycorresponding to the selected VPA output and to power off circuitrycorresponding to the remaining unselected VPA outputs. In embodiments,at any time, output select control signals 5776, 5778, 5780, 5782, and5784 ensure that circuitry corresponding to a single VPA output arepowered up, when the VPA is in transmit mode. A different digitalcontrol module embodiment may have more or less output select controlsignals depending on the particular number of VPA outputs supported bythe particular analog core implementation.

Vector MOD HI Band(s)/Vector MOD Low Band(s)n control signal 5786 isgenerated by the digital control module 5700 to indicate whether a highband frequency modulation set or a low band frequency modulation set ofvector modulators is to be used in the analog core of the VPA. In anembodiment, the high band and the low band vector modulators havedifferent characteristics, allowing each set to be more suitable for arange of modulation frequencies. Control signal 5786 is generatedaccording to the selected output of the VPA. In an embodiment, controlsignal 5786 controls circuitry within the analog core of the VPA inorder to ensure that the selected set of vector modulators is powered upand that the other set(s) of vector modulators are powered off. Inanother embodiment, control signal 5786 controls circuitry within theanalog core of the VPA in order to couple a set of interpolation filtersto the selected set of vector modulators.

3G HI Band/Normaln control signal 5788 is an optional control signalwhich may be used, if necessary, to enable the VPA to support the widerange High frequency band. In an embodiment, control signal 5788 mayforce more current through the output stage circuitry of the analog coreand/or modify the output impedance characteristics of the VPA.

Filter Response 1/Filter Response 2n control signal 5790 is an optionalcontrol signal which may be used to dynamically change the response ofinterpolation filters in the analog core of the VPA. This may be neededas the interpolation filters have different optimal responses fordifferent communication standards. For example, the optimal filterresponse has a 3 dB corner frequency around 5 MHz for WCDMA or EDGE,while this frequency is around 400 KHz for GSM. Accordingly, controlsignal 5790 allows for optimizing the interpolation filters according tothe used communication standard.

Attenuator control signals 5792 and 5794 are optional control signalswhich may be used, if necessary, to provide additional output powercontrol features and functions. For example, attenuator control signals5792 and 5794 could be configured to enable/disable RF attenuators onthe output of the VPA. These attenuators may be required based on thespecific VPA implementation, which could be fabricated using Silicon,GaAs, or CMOS processes.

FIG. 58 illustrates another exemplary digital control module 5800according to an embodiment of the present invention. Exemplary digitalcontrol module 5800 is similar in many respects to digital controlmodule 5700. In particular, both embodiments 5700, 5800 have the sameinput interface 5602, and substantial portions of the output interface(the output interface in FIG. 58 is labeled with reference number5604′). The differences between exemplary embodiments 5700 and 5800relate to the type of feedback information being provided to the digitalcontrol module. Specifically, the two embodiments 5700 and 5800 aredesigned to operate with distinctly different feedback mechanisms forerror correction. These mechanisms will be further described below inSection 4.3 with reference to the exemplary analog core implementations.

Exemplary implementation 5800 includes different input select controlsignals 5808, 5810, and 5812 compared to exemplary implementation 5700.Input select control signals 5810 and 5812 control whether feedbackinformation is to be received from the high band or the low band analogcircuitry of the VPA, depending on which band is in use. Input selectcontrol signal I/Qn 5808 controls the multiplexing of I and Q feedbackdata from the analog core of the VPA. In an embodiment, control signal5812 allows sequential switching between I data and Q data on A/D INsignal 5736.

In further distinction to exemplary embodiment 5700, exemplaryembodiment 5800 include an additional data bus 5802, which carriesdigital information from the digital control module 5800 used togenerate an automatic gain control signal 5806. Automatic gain controlsignal 5806 is used to control the gain of an amplifier circuit used inthe feedback mechanism in the analog core of the VPA. Furtherdescription of this component of the feedback mechanism will be providedbelow. In an embodiment, digital information carried by data bus 5802 isconverted from digital to analog by DAC_(—)11 to generate analog signal5806. DAC_(—)11 is controlled by a clock signal 5804 provided by thedigital control module, and is provided VREF_B signal 5739 as a centralreference voltage.

It is noted that exemplary digital control modules 5700 and 5800illustrate some of the typical input and output digital control modulesignals that may be used in a digital control module implementation.More or less input and output signals may also be used, as will beappreciated by a person skilled in the art based on the teachingsherein, depending on the system in which the VPA is being used and/orthe specific VPA analog core to be used with the digital control module.In an embodiment, exemplary digital control module implementations 5700and 5800 may be used in conjunction with a VPA analog core usingfeedback only, feedforward only, or both feedback and feedforward errorcorrection. When used in a feedforward only approach, feedback elementsand/or signals (e.g., A/D IN 5702, control signals 5738, 5740, 5742,5744, 5746, gain and phase balance control signals 5749 and 5751) may bedisabled or eliminated. Accordingly, variations of exemplary digitalcontrol module implementations 5700 and 5800 are within the scope ofembodiments of the present invention.

4.3) VPA Analog Core

In this section, various exemplary implementations of the VPA analogcore will be provided. As will be described below, the various exemplaryimplementations share a large number of components, circuits, and/orsignals, with the main differences relating to the output stagearchitecture, the adopted error correction feedback mechanism, and/orthe actual semiconductor material used in chip fabrication. As will beunderstood by a person skilled in the art based on the teachings herein,other VPA analog core implementations are also conceivable byinterchanging, adding, and/or removing features among the variousexemplary implementations described below. Accordingly, embodiments ofthe present invention are not to be limited to the exemplaryimplementations described herein.

4.3.1) VPA Analog Core Implementation A

FIG. 59 illustrates a VPA analog core implementation 5900 according toan embodiment of the present invention. In an embodiment, the inputsignals of analog core 5900 connect directly or indirectly (throughDACs) to output signals from the output interface 5604 of digitalcontrol module 5600. Similarly, feedback signals from analog core 5900connect directly or indirectly (through DACs) to the input interface ofthe digital control module 5600. For illustrative purposes, the analogcore 5900 is shown in FIG. 59 as being connected to digital controlmodule 5700, as indicated by the same numeral signals on both FIG. 57and FIG. 59.

Analog core implementation 5900 is a 2-Branch VPA embodiment. Thisimplementation 5900, however, can be readily modified to a 4-Branch or aCPCP VPA embodiment, as will be apparent to persons skilled in the artbased on the teachings herein.

At a high level, analog core 5900 includes an input stage for receivingdata signals from the digital control module 5700, a vector modulationstage for generating substantially constant envelope signals, and anamplification output stage for amplifying and outputting the desired VPAoutput signal. Additionally, analog core 5900 includes power supplycircuitry for controlling and delivering power to the different stagesof the analog core, optional output stage protection circuitry, andoptional circuitry for generating and providing feedback information tothe digital control module of the VPA.

The input stage of VPA analog core 5900 includes an optionalinterpolation filter bank (5910, 5912, 5914, and 5916) and a pluralityof switches 5964, 5966, 5968, and 5970. Interpolation filters 5910,5912, 5914, and 5916, which may also serve as anti-aliasing filters,shape the analog outputs 5753, 5755, 5757, and 5759 of DACs 01-04 togenerate the desired output waveform. In an embodiment, the response ofinterpolation filters 5910, 5912, 5914, and 5916 is dynamically changedusing control signal 5790 from the digital control module 5700. Digitalcontrol module signal 5790 may, for example, control switches withininterpolation filters 5910, 5912, 5914, and 5916 to cause a change inactive circuitry (enable/disable RC circuitry) within filters 5910,5912, 5914, and 5916. This may be needed as interpolation filters 5910,5912, 5914, and 5916 have different optimal responses for differentcommunication standards. It should be noted that interpolation filters5910, 5912, 5914, and 5916 can be implemented using digital circuitrysuch as FIR filters or programmable FIR filters. When implementeddigitally, these filters can be included within the VPA system orintegrated with a baseband processor.

Subsequently, the outputs of interpolation filters 5910, 5912, 5914, and5916 are switched using switches 5964, 5966, 5968, and 5970 to connectto either an upper band path 5964 or a lower band path 5966 of the VPAanalog core 5900. This determination between the upper and lower bandpaths is usually made by the digital control module 5700 based on theselected frequency range for transmission by the VPA. For example, thelower band path 5966 is used for GSM-900, while the upper band path 5964is used for WCDMA. In an embodiment, switches 5964, 5966, 5968, and 5970are controlled by Vector MOD HI Band(s)/Vector MOD Low Band(s)n signal5786, provided by the digital control module 5700. Signal 5786 controlsthe coupling of each of switches 5964, 5966, 5968, and 5970 torespective first or second inputs, thereby controlling the coupling ofthe outputs of interpolation filters 5910, 5912, 5914, and 5916 to theeither the upper path 5964 or lower path 5966 of the VPA analog core5900.

The vector modulation stage of VPA analog core 5900 includes a pluralityof vector modulators 5922, 5924, 5926, and 5928, divided between theupper band path 5964 and the lower band path 5966 of the analog core5900. Based on the selected band of operation, either the upper bandpath vector modulators (5922, 5924) or the lower band path vectormodulators (5926, 5928) are active.

In an embodiment, the operation of vector modulators 5922, 5924 or 5926,5928 is similar to the operation of vector modulators 1750 and 1752 inthe embodiment of FIG. 17, for example. Vector modulators 5922 and 5924(or 5926 and 5928) receive input signals 5919, 5921, 5923, and 5925(5927, 5929, 5931, and 5933) from optional interpolation filters 5910,5912, 5914, and 5916, respectively. Input signals 5919, 5921, 5923, and5925 (or 5927, 5929, 5931, and 5933) include amplitude information thatis used to generate the constant envelope signals by the vectormodulators. Further, vector modulators 5922 and 5924 (or 5926 and 5928)receive a HI Band RF CLK signal 5935 (LOW BAND RF_CLK signal 5937) froma HI Band(s) Frequency Synthesizer 5918 (Low Band(s) FrequencySynthesizer 5920). HI Band(s) Frequency Synthesizer 5918 (Low Band(s)Frequency Synthesizer 5920) are optionally located externally or in theVPA analog core. In an embodiment, HI Band(s) Frequency Synthesizer 5918(Low Band(s) Frequency Synthesizer 5920) generates RF frequencies in theupper band range of 1.7-1.98 GHz (lower band range of 824-915 MHz). Inanother embodiment, HI Band(s) Frequency Synthesizer 5918 and LowBand(s) Frequency Synthesizer 5920 are controlled by digital controlmodule signals 5796 and 5798, respectively. Signals 5796 and 5798, forexample, power up the appropriate frequency synthesizer according to theselected transmission frequency band, and instruct the selectedsynthesizer to generate a RF frequency clock according to the selectedtransmission frequency.

Vector modulators 5922 and 5924 (or 5926 and 5928) modulate inputsignals 5919, 5921, 5923, and 5925 (5927, 5929, 5931, and 5933) with HIBAND RF_CLK signal 5935 (LOW BAND RF_CLK signal 5937). In an embodiment,vector modulators 5922 and 5924 (or 5926 and 5928) modulate the inputsignals with appropriately derived and/or phase shifted versions of HIBAND RF_CLK signal 5935 (LOW BAND RF_CLK signal 5937), and combine thegenerated modulated signals to generate substantially constant envelopesignals 5939 and 5941 (5943 and 5945).

In another embodiment, vector modulators 5922 and 5924 (or 5926 and5928) further receive a phase balance control signal 5751 from the VPAdigital control module. Phase balance control signal 5751 controlsvector modulators 5922 and 5924 (or 5926 and 5928) to cause a change inphase in constant envelope signals 5939 and 5941 (or 5943 and 5945), inresponse to phase feedback information from the analog core. Theamplitude and phase feedback mechanism is further discussed below.Optionally, upper band path vector modulators 5922 and 5924 also receivea 3G HI Band/Normaln signal 5788 from the digital control module. Signal5788 can be used, if necessary, to further support driving the vectormodulators at the highest frequencies of the upper band.

The output stage of VPA analog core 5900 includes a plurality of MISOamplifiers 5930 and 5932, divided between the upper band path 5964 andthe lower band path 5966 of the analog core 5900. Based on the selectedband of operation, either the upper band path MISO amplifier 5930 or thelower band path MISO amplifier 5932 is active.

In an embodiment, MISO amplifier 5930 (or 5932) receives substantiallyconstant envelope signals 5939 and 5941 (or 5943 and 5945) from vectormodulators 5922 and 5924 (or 5926 and 5928). MISO amplifier 5930 (or5932) individually amplifies signals 5939 and 5941 (or 5943 and 5945) togenerate amplified signals, and combines the amplified signals togenerate output signal 5947 (or 5949). In an embodiment, MISO amplifier5930 (or 5932) combines the amplified signals via direct coupling, asdescribed herein. Other modes of combining the amplified signalsaccording to embodiments of the present invention have been describedabove in Section 3.

The output stage of VPA analog core 5900 is capable of supportingmulti-band multi-mode VPA operation. As shown in FIG. 59, the outputstage includes two MISO amplifiers 5930 and 5932 for upper band andlower band operation, respectively. In addition, the output of each ofthe upper band 5964 and the lower band 5966 is further switched betweenone or more output paths according to the selected transmission mode(e.g., GSM, WCDMA, etc.). Typically, separate output paths are neededfor different transmission modes since FDD-based modes (e.g., WCDMA)require the presence of duplexers at the output, while TDD-based modes(e.g., GSM, EDGE) have T/R switched outputs.

In analog core 5900, the output 5947 of MISO amplifier 5930 can becoupled to one of three output paths 5954, 5956, and 5958, with eachoutput path 5954, 5956, 5958 being the one that is coupled to an antenna(not shown) or connector (not shown) for a particular mode oftransmission. Similarly, the output 5949 of MISO amplifier 5932 can becoupled to one of two output paths 5960 and 5962. In an embodiment,output select signals 5776, 5778, 5780, 5782, and 5784, provided by thedigital control module, control switches 5942 and 5944 to couple theoutput of the active MISO amplifier to the appropriate output path,based on the selected transmission mode. It is noted that more or lessoutput paths 5954, 5956, 5958, 5960, and 5962 may be used.

Accordingly, with only two MISO amplifiers 5930 and 5932, analog core5900 supports multiple different transmission modes. In an embodiment,analog core 5900 allows for using a single MISO amplifier to supportGSM, EDGE, WCDMA, and CDMA2000. It is clear therefore that one of theadvantages of this exemplary VPA analog core according to implementation5900 is in the reduction in the number of PAs per supported output pathsThis directly corresponds to a reduction in required chip area for theVPA analog core 5900.

In an embodiment, the output stage of analog core 5900 receives optionaloutput stage autobias signal 5761, driver stage autobias signal 5763,and gain balance control signal 5749 from the digital control module.Output stage autobias signal 5761 and driver stage autobias signal 5763may or may not be needed according to the particular type of transistorsused in the actual MISO implementation. In an embodiment, output stageautobias signal 5761 and driver stage autobias signal 5763 control thebias of MISO amplification stages to cause a change in the power outputand/or the power efficiency of the VPA. Similarly, gain balance controlsignal 5749 may cause a change in the gain levels of different MISOamplification stages, in response to power output feedback informationreceived by the digital control module from the analog core. Furtherdiscussion of these optional output stage input signals will be providedbelow.

In an embodiment, the output stage of analog core 5900 provides optionalfeedback signals to the digital control module 5700 of the VPA.Typically, these feedback signals are used by the digital control module5700 to correct for amplitude and phase variations in branches of theVPA and/or for controlling the output power of the VPA. In the specificimplementation of analog core 5900, a differential feedback approach isemployed to monitor for amplitude and phase variations, using adifferential branch amplitude signal 5950 and a differential branchphase signal 5948 provided by the output stage. Further, output powermonitoring is provided using signals PWR Detect A 5938 and PWR Detect B5940, which measure the output power of MISO amplifiers 5930 and 5932,respectively. Since only one of MISO amplifiers 5930 and 5932 can beactive at any time, in an embodiment, PWR Detect A 5938 and PWR Detect5940 are summed together using summer 5942, to generate a signal thatcorresponds to the output power of the VPA.

In an embodiment, the feedback signals from the output stage aremultiplexed using an input selector 5946 controlled by the digitalcontrol module 5700. In another embodiment, the digital control module5700 uses A/D Input Selector signals 5738, 5740, 5742, 5744, and 5746 tocontrol input selector 5946 and select the feedback signal to bereceived. It is noted that monitoring of feedback signals may not needto occur in real-time rate and may only need to be performedperiodically at a low rate. For example, for the purpose of branchamplitude and phase error correction, the rate at which feedbackmonitoring is performed depends on several factors such as the degree offeedforward correction being performed in the digital control module,process variations due to temperature, or operation changes such aschanging battery or supply voltages.

Above, the tradeoffs between feedforward and feedback error compensationand/or correction techniques have been described. Accordingly,parameters governing the rates at which feedback monitoring is performedare design choices typically selected by the actual designer of the VPA.As a result, analog core implementation 5900 can be programmed tooperate as a pure feedback implementation by disabling any feedforwardcorrection in the digital control module, a pure feedforwardimplementation by disabling the monitoring of feedback signals, or as ahybrid feedforward/feedback implementation with variablefeedforward/feedback utilization.

In an embodiment, the output stage of analog core 5900 includes optionaloutput stage protection circuitry. In FIG. 59, this is illustrated usingVSWR (Voltage-Standing-Wave-Ratio) Protect circuitry 5934 and 5936coupled respectively to MISO amplifiers 5930 and 5932. VSWR protectioncircuitry 5934, 5936 may or may not be needed depending on the actualMISO amplifier implementation. In an embodiment, VSWR Protect circuitry5934 and 5936 protect the output stage PAs (see PAs 6030 and 6032 inFIG. 60, for example) from going into thermal shutdown or devicebreakdown, when the output voltage level could cause the output stagebreakdown voltage to be exceeded. In conventional systems, this isachieved by using an RF isolator at the output of the PAs, which is bothexpensive and lossy (typically causes around 1.5 dB in power loss).Accordingly, VSWR Protect circuitry 5934, 5936 eliminate the need forisolators at the output stage, further reducing the cost, size, andpower loss of the VPA. In an embodiment, VSWR Protect circuitry 5934,5936 enable an isolator-free output stage capable of supporting WCDMA.VSWR protection circuitry 5934 and 5936 also enable the VPA to operateinto any VSWR level without damaging the VPA. VSWR protection circuitrycan be designed to deliver the maximum output power of a particularimplementation of a VPA into any VSWR level.

As described above, analog core 5900 includes power supply circuitry forcontrolling and delivering power to the different stages of the analogcore 5900. In one aspect, the power supply circuitry provides means forpowering up active portions of the VPA analog core 5900. In anotheraspect, the power supply circuitry provides means for controlling thepower efficiency and/or the output power of the VPA.

In analog core implementation 5900, the power supply circuitry includesMA Power Supply 5902, Driver Stage Power Supply 5904, Output Stage PowerSupply 5906, and Vector Mods Power Supply 5908. In an embodiment, thepower supply circuitry is controlled by output select signals 5776,5778, 5780, 5782, and 5784, provided by the digital control module 5700.

MA Power Supply 5902 includes circuitry for controlling the powering upof active portions of the VPA analog core 5900. In analog core 5900, MAPower Supply 5902 has two outputs MA1 VSUPPLY 5903 and MA2 VSUPPLY 5905.At any time, only one of MA1 VSUPPLY 5903 or MA2 VSUPPLY 5905 is active,ensuring that only the upper band 5964 or the lower band 5966 portion ofthe VPA analog core 5900 is powered up. In an embodiment, the activeoutput of MA Power Supply 5902 is coupled to all active circuitry of theVPA analog core 5900, with the exception of circuitry having uniquepower supply signals as described below. MA Power Supply 5902 receivesoutput select signals from the digital control module, which enable oneor the other of output signals MA1 VSUPPLY 5903 or MA2 VSUPPLY 5905,based on the selected output of the VPA.

Driver Stage Power Supply 5904 includes circuitry for providing power tothe driver stage circuitry of the MISO amplifiers 5930, 5932. Similar toMA Power Supply 5902, Driver Stage Power Supply 5904 has two outputs MA1Driver VSUPPLY 5907 and MA2 Driver VSUPPLY 5909, with only one of thetwo outputs being active at any time. Driver Stage Power Supply 5904 isalso controlled by output select signals 5776, 5778, 5780, 5782, and5784 according to the selected output of the VPA. In addition, DriverStage Power Supply 5904 receives a Driver Stage Voltage Control signal5767 from the digital control module 5700. In an embodiment, the outputsMA1 Driver VSUPPLY 5907 and MA2 Driver VSUPPLY 5909 are generatedaccording to the received Driver Stage Voltage Control signal 5767. Inanother embodiment, Driver Stage Voltage Control signal 5767 causesDriver Stage Power Supply 5904 to increase or decrease MA1 DriverVSUPPLY 5907 or MA2 Driver VSUPPLY 5909 to control the driver stagepower amplification level. In another embodiment, Driver Stage VoltageControl signal 5767 is used by the digital control module 5700 to affecta change, using Driver Stage Power Supply 5904, in the power supplyvoltage of the driver stage of the active MISO amplifier 5930 or 5932,thereby controlling the power efficiency of the VPA.

Output Stage Power Supply 5906 includes circuitry for providing power tothe PA stage circuitry of the MISO amplifiers 5930, 5932. Similar to MAPower Supply 5902, Output Stage Power Supply 5906 has two outputs MA1Output Stage VSUPPLY 5911 and MA2 Output Stage VSUPPLY 5913, with onlyone of the two outputs being active at any time. Output Stage PowerSupply 5906 is also controlled by output select signals 5776, 5778,5780, 5782, and 5784 according to the selected output of the VPA. Inaddition, Output Stage Power Supply 5906 receives an Output StageVoltage Control signal 5765 from the digital control module 5700. In anembodiment, the outputs MA1 Output Stage VSUPPLY 5911 and MA2 OutputStage VSUPPLY 5913 are generated according to the received Output StageVoltage Control signal 5765. In another embodiment, Output Stage VoltageControl signal 5765 causes Output Stage Power Supply 5906 to increase ordecrease MA1 Output Stage VSUPPLY 5911 or MA2 Output Stage VSUPPLY 5913to control the PA stage power amplification level. In anotherembodiment, Output Stage Voltage Control signal 5765 is used by thedigital control module 5700 to affect a change, using Output Stage PowerSupply 5906, in the power supply voltage of the PA stage of the activeMISO amplifier 5930 or 5932, thereby controlling the power efficiency ofthe VPA.

Vector Mods Power Supply 5908 includes circuitry for providing power tothe vector modulators 5922, 5924, 5926, and 5928 of the analog core5900. In analog core 5900, Vector Mods Power Supply 5908 has two outputs5915 and 5917 for powering up the upper band vector modulators 5922 and5924 and the lower band vector modulators 5926 and 5928, respectively.At any time, only one of outputs 5915 or 5917 is active, ensuring thatonly the upper band or the lower vector modulators of the analog core5900 are powered up. Vector Mods Power Supply 5908 receives a vector modselect signal 5786 from the digital control module 5700, which controlswhich of its two outputs 5915 and 5917 is active, according to theselected transmission frequency requirements.

In addition to the above described power supply circuitry, analog core5900 may optionally include voltage reference generator circuitry. Thevoltage reference generator circuitry may reside externally or withinthe VPA analog core 5900. The voltage reference generator circuitrygenerates reference voltages for different circuits within the VPA. Inan embodiment, as illustrated in FIG. 57, the voltage referencegenerator circuitry provides reference voltages to DACs 01-10, coupledto data outputs of the digital control module. In another embodiment, asillustrated in FIG. 59, the voltage reference generator circuitryprovides reference voltages to the interpolation filters and/or thevector modulators in the VPA analog core. In an embodiment, circuits ofthe same branch of the VPA are provided with the same reference voltage.For example, note that DACs 01 and 02, interpolation filters 5910 and5912, and vector modulators 5922 and 5924, which represent a VPA branchor data path, all share the same reference voltage VREF_C 5741. Fordifferent implementations and system performance requirements, thevoltage reference signals can be provided as a single reference voltageor multiple reference voltages.

FIG. 60 illustrates an output stage embodiment 6000 according to VPAanalog core implementation 5900. Output stage embodiment 6000 includes aMISO amplifier stage 6058, an optional output switching stage (embodiedby switch 6044), and optional output stage protection and powerdetection circuitry.

In an embodiment, MISO amplifier stage 6058 corresponds to MISOamplifier 5930 in analog core 5900. Accordingly, MA VSUPPLY signal 6006,MA Driver VSUPPLY signal 6004, and MA Output Stage VSUPPLY signal 6002correspond respectively to signals 5903, 5907, and 5911 in FIG. 59.Similarly, MA IN1 and MA IN2 input signals 6008 and 6010 and MA Outputsignals 6046, 6048, and 6050 correspond respectively to MISO inputsignals 5939 and 5941 and output signals 5954, 5956, and 5958 in FIG.59. PWR Detect signal 6023 corresponds to PWR Detect A signal 5938 inFIG. 59. (Generally, implementation of MISO amplifier 5932 could also bebased on MISO amplifier stage 6058 in FIG. 60.)

MISO amplifier stage 6058 in embodiment 6000 includes a pre-driveramplification stage, embodied by Pre-Drivers 6012 and 6014, a driveramplification stage, embodied by Drivers 6018 and 6020, and a PAamplification stage, embodied by output stage PAs 6030 and 6032. In anembodiment, substantially constant envelope input signals MA IN1 6008and MA IN2 6010 are amplified at each stage of MISO amplifier 6058,before being summed at the outputs of the PA stage.

In an embodiment, MISO amplifier stage 6058 is powered by power supplysignals provided by voltage controlled power supply circuits. Asdescribed with reference to FIG. 59, the power supply signals aregenerated by power supply circuitry of the VPA analog core 5900. In anembodiment, the power supply signals are used to control the powersupply voltages of the different amplification stages of MISO amplifierstage 6058, thereby affecting the power efficiency of the VPA undervarious operating conditions. In another embodiment, the power supplysignals are used to control the gain of each of the differentamplification stages of MISO amplifier stage 6058, thereby enabling apower control mechanism. Further, the power supply signals can becontrolled independently of each other, allowing for independent controlof power and/or efficiency for each of the different amplificationstages of MISO amplifier stage 6058. This independent control allows,for example, for shutting off one or more amplification stages of MISOamplifier 6058 according to the desired output power of the VPA. In FIG.60, the power supply signals are illustrated using signals 6002, 6004,and 6006.

In an embodiment, MISO amplifier stage 6058 includes bias controlcircuitry.

The bias control circuitry may be optional according to the particularMISO amplifier implementation. In an embodiment, the bias controlcircuitry provides a mechanism for controlling efficiency and/or powerat each amplification stage of MISO amplifier 6058. This mechanism isindependent of the mechanism described above with reference to the powersupply signals. Further, this mechanism provides for independently andindividually controlling each amplification stage. In FIG. 60, the biascontrol circuitry is illustrated using Gain Balance Control Circuitry6016, Driver Stage Autobias Circuitry 6022, and Output Stage AutobiasCircuitry 6028.

In an embodiment, Gain Balance Control Circuitry 6016 is coupled to theinputs of the pre-driver amplification stage as illustrated in FIG. 60.Gain Balance Control Circuitry 6016 receives a Gain Balance Controlsignal 5749 from the digital control module 5700 (through a DAC), andoutputs input bias control signals 6013 and 6015. Driver Stage AutobiasCircuitry 6022 is coupled to the inputs of the driver amplificationstage as illustrated in FIG. 60. Driver Stage Autobias Circuitry 6022receives Driver Stage Autobias signal 5763 from the digital controlmodule 5700 (through a DAC), and outputs input bias control signals 6017and 6019. Similarly, Output Stage Autobias Circuitry 6028 is coupled tothe inputs of the PA amplification stage as illustrated in FIG. 60.Output Stage Autobias Circuitry 6028 receives Output Stage Autobiassignal 5761 from the digital control module 5700 (through a DAC), andoutputs input bias control signals 6029 and 6031.

In an embodiment, the digital control module 5700 independently controlsthe bias of the pre-driver stage, the driver stage, and the PA stage ofMISO amplifier 6058 using Gain Balance Control signal 5749, Driver StageAutobias signal 5763, and Output Stage Autobias signal 5761,respectively. In another embodiment, the digital control module 5700 mayaffect a change in the bias of the pre-driver stage, the driver stage,and/or the PA stage of MISO amplifier 6058 only using Gain BalanceControl signal 5749. As illustrated in FIG. 60, Gain Balance ControlCircuitry 6016 is coupled to Driver Stage Autobias Circuitry 6022 andOutput Stage Autobias Circuitry 6028. In an embodiment, a change in theoverall gain of the VPA is affected by digital control module 5700 firstby controlling the bias at the pre-driver stage. If further gain changeis needed, bias control is performed at the driver stage, andsubsequently at the PA stage.

In an embodiment, MISO amplifier stage 6058 includes circuits forenabling an error correction and/or compensation feedback mechanism. Inoutput stage embodiment 6000, a differential feedback mechanism isadopted, whereby Differential Branch Amplitude Measurement Circuitry6024 and Differential Branch Phase Measurement Circuitry 6026respectively measure differences in amplitude and phase between branchesof MISO amplifier 6058. In an embodiment, Differential Branch AmplitudeMeasurement Circuitry 6024 and Differential Branch Phase MeasurementCircuitry 6026 are coupled at the inputs of the PA stage (PAs 6030 and6032) of MISO amplifier 6058. In other embodiments, circuitry 6024 and6026 may be coupled at the inputs of prior stages of MISO amplifier6058. In an embodiment, Differential Branch Amplitude MeasurementCircuitry 6024 and Differential Branch Phase Measurement Circuitry 6026respectively output Differential Branch Amplitude signal 5950 andDifferential Branch Phase signal 5948, which are fed back to digitalcontrol module 5700 (through A/D converters). Since digital controlmodule 5700 knows at any particular time the correct differences inamplitude and/or phase between the branches of MISO amplifier 6058, itmay determine any errors in amplitude and/or phase based on DifferentialBranch Amplitude signal 5950 and Differential Branch Phase signal 5948.

Output stage embodiment 6000 includes optional output stage protectioncircuitry. The output stage protection circuitry may or may not beneeded according to the particular MISO amplifier implementation. InFIG. 60, the output stage protection circuitry is illustrated using VSWRProtection Circuitry 6034. In an embodiment, VSWR Protection Circuitry6034 monitors the output of the PA stage, and controls the gain of MISOamplifier 6058 to protect PAs 6030 and 6032. In embodiment 6000, VSWRProtection Circuitry 6034 receives a signal 6036, which is coupledeither directly or indirectly to the output of the PA stage. In anembodiment, VSWR Protection Circuitry 6034 ensures that the voltagelevel at the output of the PA stage remains below a certain level, toprevent PAs 6030 and 6032 from going into thermal shutdown orexperiencing device breakdown. In an embodiment, VSWR ProtectionCircuitry 6034 ensures that a breakdown voltage of PAs 6030 and 6032 isnot exceeded. Accordingly, whenever the voltage level at the output ofPAs 6030 and 6032 is above a pre-determined threshold, VSWR ProtectionCircuitry 6034 may cause a decrease in the gain of the MISOamplification stages. In an embodiment, VSWR Protection Circuitry 6034is coupled to Balance Gain Control Circuitry 6016, which in turn iscoupled to both Driver Stage Autobias Circuitry 6022 and Output StageAutobias Circuitry 6028. In an embodiment, VSWR Protection Circuitry6034 responds to a pre-determined voltage level at the output stage PAsby decreasing gain first at the pre-driver stage, then at the driverstage, and finally at the PA stage. As described above, VSWR ProtectionCircuitry 6034 may or may not be needed according to the particular MISOamplifier implementation. For example, a GaAs (Gallium Arsenide) MISOamplifier implementation would not require VSWR Protection Circuitry, astypical breakdown voltages of GaAs transistors are too large to beexceeded in many RF scenarios.

Output stage embodiment 6000 includes optional power detectioncircuitry. In an embodiment, the power detection circuitry serves as ameans for providing power level feedback to the digital control module.In FIG. 60, the power detection circuitry is illustrated using PowerDetection Circuitry 6038. In an embodiment, Power Detection Circuitry6038 is coupled to the output of the PA stage of MISO amplifier 6058.Power Detection Circuitry 6038 may be coupled directly or indirectly tothe output of the PA stage as illustrated by signal 6040 in FIG. 60. Inan embodiment, Power Detection Circuitry 6038 outputs a PWR Detectsignal 6023. PWR Detect signal 6023 may be equivalent to PWR Detect Asignal 5938 or PWR Detect B signal 5940 shown in FIG. 59, which are fedback (through A/D converters) into the digital control module of theVPA. The digital control module uses PWR Detect signal 6023 to regulatethe output power of the VPA as desired.

The optional output switching stage of output stage embodiment 6000 isembodied by a switch 6044 in FIG. 60. In an embodiment, switch 6044 iscoupled to one of three outputs 6046, 6048, or 6050 of the VPA. Asdescribed earlier, the switch is controlled by a set of output selectsignals 5776, 5778, and 5780, provided by the digital control module.Switch 6044 is coupled to the proper output according to the selecttransmission mode and/or desired output frequency requirements (e.g.,GSM, WCDMA, etc.).

Accordingly, pull-up impedance coupling at the output of the VPA can bedone in various ways. In an embodiment, as shown in FIG. 60, pull-upimpedances 6052, 6054, and 6056 are respectively coupled between outputs6046, 6048, and 6050 and MA Output Stage VSUPPLY 6002. In anotherembodiment, a single pull-up impedance is used and is coupled betweenthe output 6042 of the PA stage and MA Output Stage VSUPPLY 6002. Theadvantage of the first approach lies in that, by placing thepull-impedance after the switch 6044, the impedance characteristics ofswitch 6044 can be taken into account when selecting values forimpedances 6052, 6054, and/or 6056, allowing the VPA designer to exploita further aspect to increase the efficiency of the VPA. On the otherhand, the second approach requires a smaller number of pull-upimpedances.

According to the particular MISO amplifier implementation, output stageembodiment 6000 may include more or less circuitry than to what isillustrated in FIG. 60.

According to embodiments of the present invention, output stageembodiment 6000 including MISO amplifier stage 6058, the optional outputswitching stage (switch 6044), and the optional output protection andpower detection circuitry may be fabricated using a SiGe(Silicon-Germanium) material. In another embodiment, MISO amplifierstage 6058 is fabricated using SiGe, and the output switching stage isfabricated using GaAs. In another embodiment, the PA stage (PAs 6030 and6032) and the output switching stage are fabricated using GaAs, whileother circuitry of MISO amplifier stage 6058 and optional circuitry ofthe output stage are fabricated using SiGe. In another embodiment, thePA stage, the driver stage, and the output switching stage arefabricated using GaAs, while other circuitry of MISO amplifier stage6058 and optional circuitry of the output stage are fabricated usingSiGe. In another embodiment, the PA stage, the driver stage, thepre-driver stage, and the output switching stage are fabricated usingGaAs. In another embodiment, the VPA system may be implemented usingCMOS for all circuitry except for the output stage (6030 or 6032) whichcould be implemented in SiGe or GaAs material. In another embodiment,the VPA system may be implemented in its entirety in CMOS. Othervariations and/or combinations of fabrication material(s) used forcircuitry of the output stage are also possible, as can be understood bya person skilled in the art, and are therefore also within the scope ofembodiments of the present invention.

Accordingly, as different semiconductor materials have different costsand performance, embodiments of the present invention provide a varietyof VPA designs encompassing a wide range of cost and performanceoptions.

4.3.2) VPA Analog Core Implementation B

FIG. 61 illustrates an alternative VPA analog core implementation 6100according to an embodiment of the present invention. For illustrativepurposes, the VPA analog core 6100 is shown in FIG. 61 as beingconnected to digital control module 5700, although alternatively otherdigital control modules could be used. The physical connection betweenanalog core 6100 and digital control module implementation 5700 isillustrated in FIG. 61, as indicated by the same numeral signals on bothFIG. 57 and FIG. 61.

Analog core implementation 6100 is corresponds to a 2-Branch VPAembodiment. This implementation, however, can be readily modified to a4-Branch or a CPCP VPA embodiment, as will be apparent to personsskilled in the art based on the teachings herein.

Analog core implementation 6100 has the same input stage and vectormodulation stage as analog core implementation 5900, described above.Accordingly, similar to analog core implementation 5900, analog core6100 includes an upper band path 5964 and a lower band path 5966 forupper band and lower band operation of the VPA, respectively.

One of the differences between analog core 5900 and analog core 6100lies in the output stage of the VPA. In contrast to the output stage ofanalog core 5900, which includes two MISO amplifiers 5930 and 5932, theoutput stage of analog core 6100 includes five MISO amplifiers 6126,6128, 6130, 6132, and 6134, divided between the upper band path 5964 andthe lower band path 5966 of the analog core. In an embodiment, theoutput stage includes a combination of SiGe and GaAs MISO amplifiers. Inan embodiment, the upper band path 5964 includes three MISO amplifiers6126, 6128, and 6130, and the lower band path 5966 includes two MISOamplifiers 6132 and 6134. Based on the selected band of operation, asingle MISO amplifier, either in the upper band path 5964 or the lowerband path 5966, is active. In an embodiment, each of MISO amplifiers6126, 6128, 6130, 6132, and 6134 can be dedicated to a singletransmission mode (e.g., WCDMA, GSM, EDGE, etc.) of the VPA. This is incontrast to analog core 5900, where each of MISO amplifiers 5930 and5932 supports more than one transmission modes. Advantages anddisadvantages of each architecture will be further discussed below.

As a result of having more than one MISO amplifiers per path, aswitching stage is needed to couple the vector modulation stage to theMISO amplifiers in analog core 6100. In FIG. 61, this is illustratedusing switches 6118, 6120, 6122, and 6124. In an embodiment, accordingto the selected transmission mode, switches 6118 and 6120 couple theoutputs 5939 and 5941 of vector modulators 5922 and 5924 to one of MISOamplifiers 6126, 6128, and 6130. Similarly, switches 6122 and 6124couples the outputs 5943 and 5945 to one of MISO amplifiers 6132 and6134, according to the selected transmission mode and/or frequencyrequirements.

In an embodiment, MISO amplifier 6126 (or 6128, 6130, 6132, 6134)receives constant envelope signals 6119 and 6121 (or 6123 and 6125, 6127and 6129, 6131 and 6133, 6135 and 61137). MISO amplifier 6126 (or 6128,6130, 6132, 6134) individually amplifies signals 6119 and 6121 (or 6123and 6125, 6127 and 6129, 6131 and 6133, 6135 and 6137) to generateamplified signals, and combines the amplified signals to generate outputsignal 6141 (6144, 6146, 6148, 6150). In an embodiment, MISO amplifier6126 (or 6128, 6130, 6132, 6134) combines the amplified signals viadirect coupling, as described herein. Other modes of combining theamplified signals according to embodiments of the present invention havebeen described above in Section 3.

The output stage of VPA analog core 6100 is capable of supportingmulti-band multi-mode VPA operation. Further, since the output stage ofanalog core 6100 can dedicate one MISO amplifier for each supportedtransmission mode, the output switching stage (embodied in analog core5900 by switches 5942 and 5944) can be eliminated. This results in amore efficient output stage (no power loss due switching stage), but atthe expense of a larger chip area. This summarizes the main tradeoffbetween the architecture of analog core 5900 and that of analog core6100.

In an embodiment, the output stage of analog core 6100 receives optionalbias control signals from digital control module 5700. These are outputstage autobias signal 5761, driver stage autobias signal 5763, and gainbalance control signal 5749, which have been described above withreference to analog core 5900.

In an embodiment, the output stage of analog core 6100 provides optionalfeedback signals to digital control module 5700 of the VPA. Thesefeedback signals include Differential Branch Amplitude signal 5950 andDifferential Branch Phase signal 5948, described above with reference toanalog core 5900, to enable a differential feedback approach to monitorfor amplitude and phase variations in branches of the VPA. Also, similarto analog core 5900, output power monitoring is provided using PWRDetect signals 6152, 6154, 6156, 6158, and 6160, each of which measuringone of outputs 6142, 6144, 6146, 6148, and 6150 of the VPA. Since onlyone of the VPA outputs can be active at any time, PWR Detect signals6152, 6154, 6156, 6158, and 6160 are summed together, in an embodiment,using summer 5952, to generate a signal that corresponds to the currentoutput power of the VPA.

Similar to analog core 5900, the feedback signals from the output stageare multiplexed using an input selector 5946 controlled by the digitalcontrol module. Other aspects of the multiplexing of the feedbacksignals are described above with reference to analog core 5900.

Similar to analog core 5900, analog core 6100 can be designed to operateas a pure feedback implementation by disabling any feedforwardcorrection in the digital control module, a pure feedforwardimplementation by disabling the monitoring of feedback signals, or as ahybrid feedforward/feedback implementation with variablefeedforward/feedback utilization.

In an embodiment, the output stage of analog core 6100 includes optionaloutput stage protection circuitry. In FIG. 61, this is illustrated usingVSWR (Voltage-Standing-Wave-Ratio) Protect circuitry 6136, 6138, and6140 coupled respectively to MISO amplifiers 6128, 6130, and 6134. VSWRprotection circuitry may or may not be needed depending on the actualMISO amplifier implementation. For example, note that MISO amplifiers6126 and 6132, which are GaAs amplifiers, require no VSWR protectioncircuitry for many applications. Functions and advantages of VSWRProtection circuitry according to embodiments of the present inventionare described above with reference to analog core 5900.

Analog core 6100 includes power supply circuitry for controlling anddelivering power to the different stages of the analog core. In oneaspect, the power supply circuitry provides means for powering up activeportions of the VPA analog core. In another aspect, the power supplycircuitry provides means for controlling the power efficiency and/or theoutput power of the VPA.

The power supply circuitry of analog core 6100 is substantially similarto the power supply circuitry of analog core 5900, with the differencebeing that analog core 6100 includes five MISO amplifiers as opposed totwo in analog core 5900. In FIG. 61, the power supply circuitry isembodied in GMA and MA Power Supply circuitry 6102, Driver Stage PowerSupply circuitry 5904, Output Stage Power Supply circuitry 5908, andVector Mods Power Supply circuitry 5908. Each of circuitry 6102, 5904,and 5906 has five output power supply signals, with a single one ofthese five output signals being active at any time, according to theactive MISO amplifier of the VPA. Function and operation of the powersupply circuitry of analog core 6100 are substantially similar to thoseof the power supply circuitry of analog core 5900, described above.

FIG. 62 illustrates an output stage embodiment 6200 according to VPAanalog core implementation 6100. Output stage embodiment 6200 includes aMISO amplifier stage 6220 and optional output stage protection and powerdetection circuitry.

MISO amplifiers 6126, 6128, 6130, 6132 and/or 6134 shown in FIG. 61 canbe implemented using an amplifier such as MISO amplifier stage 6220.

Output stage embodiment 6200 is substantially similar to output stageembodiment 6000 illustrated in FIG. 60, with the main difference beingin the elimination of the output switching stage (embodied by switch6044 in FIG. 60) in embodiment 6200.

Similar to embodiment 6000, MISO amplifier stage 6220 in embodiment 6200includes a pre-driver amplification stage, embodied by Pre-Drivers 6206and 6208, a driver amplification stage, embodied by Drivers 6210 and6212, and a PA amplification stage, embodied by output stage PAs 6214and 6216. In an embodiment, substantially constant envelope inputsignals MA IN1 6202 and MA IN 6204 are amplified at each stage of MISOamplifier 6220, before being summed at the outputs of the PA stage.Input signals MA IN1 6202 and MA IN 6204 correspond to signals 6123 and6125 in FIG. 61, for example.

In an embodiment, MISO amplifier stage 6220 of output stage embodiment6200 is powered by power supply signals provided by voltage controlledpower supply circuits. In another embodiment, MISO amplifier stage 6220includes optional bias control circuitry controllable by the digitalcontrol module. In another embodiment, MISO amplifier stage 6220includes circuits for enabling an error correction and/or compensationfeedback mechanism. In another embodiment, output stage embodiment 6000includes optional output stage protection circuitry and power detectioncircuitry. These aspects (power supply, bias control, error correction,output protection, and power detection) of output stage embodiment 6200are substantially similar to what have been described above with respectto output stage embodiment 6000.

According to embodiments of the present invention, output stageembodiment 6200 may be fabricated using a SiGe (Silicon-Germanium)material including MISO amplifier stage 6220 and the optional outputprotection and power detection circuitry. In another embodiment, MISOamplifier stage 6220 is fabricated using SiGe in its entirety. Inanother embodiment, the PA stage (PAs 6214 and 6216) of MISO amplifierstage 6220 is fabricated using GaAs, while other circuitry of MISOamplifier stage 6220 and optional circuitry of the output stage arefabricated using SiGe. In another embodiment, the PA stage and thedriver stage (Drivers 6210 and 6212) of MISO amplifier stage 6220 arefabricated using GaAs, while other circuitry of MISO amplifier stage6220 and optional circuitry of the output stage are fabricated usingSiGe. In another embodiment, the PA stage, the driver stage, and thepre-driver stage (Pre-Drivers 6206 and 6208) are fabricated using GaAs.In another embodiment, the VPA system may be implemented using CMOS forall circuitry except for the output stage (6030 or 6032) which could beimplemented in SiGe or GaAs material. In another embodiment, the VPAsystem may be implemented in its entirety in CMOS. Other variationsand/or combinations of fabrication material(s) used for circuitry of theoutput stage are also possible, as can be understood by a person skilledin the art, and are therefore also within the scope of embodiments ofthe present invention. Further, output stages within the same the VPAmay be fabricated using different material, as illustrated in FIG. 61for example, where MISO amplifiers 6128, 6130, and 6134 are SiGeamplifiers and MISO amplifiers 6126 and 6132 are GaAs amplifiers (one ormore stages of their output stage are GaAs).

4.3.3) VPA Analog Core Implementation C

FIG. 63 illustrates another VPA analog core implementation 6300according to an embodiment of the present invention. For illustrativepurposes, example analog core 6300 is shown in FIG. 63 as beingconnected to digital control module 5800, although other digital controlmodules could alternatively be used. The physical connection betweenanalog core 6300 and digital control module 5800 is indicated by thesame numeral signals on both FIG. 58 and FIG. 63.

Analog core implementation 6300 corresponds to a 2-Branch VPAembodiment. This implementation, however, can be readily modified to a4-Branch or a CPCP VPA embodiment, as will be apparent to a personskilled in the art based on the teachings herein.

Analog core implementation 6300 includes similar input stage, vectormodulation stage, and amplification output stage as analog core 5900 ofFIG. 59. Function, operation and control of these stages is describedabove with reference to FIG. 59.

Similar to analog core 5900, analog core 6300 includes a feedback errorcorrection and/or compensation mechanism. In contrast to analog core5900, however, analog core 6300 employs a receiver-based feedbackmechanism, as opposed to a differential feedback mechanism in analogcore 5900. A receiver-based feedback mechanism is one that is based onhaving a receiver that receives the active output of the VPA, generatesI data and Q data from the received output, and feeds back the generatedI and Q data to the digital control module. By estimating the delaybetween the input and the output of the VPA, the feedback I and Qsignals can be properly aligned with their corresponding input I and Qsignals. In another embodiment, the receiver feedback includes thecomplex output signal (magnitude and phase polar information) instead ofCartesian I and Q data signals.

In an embodiment, this is done by coupling a receiver (not shown) at theactive output of the VPA (5947 or 5949). In FIG. 63, signals 6302 and6304 respectively represent upper band and lower band RF inputs into thereceiver. Only one of signals 6302 and 6304 can be active at any time,depending on whether the upper band path 5964 or the lower band path5966 of analog core 6300 is being used. Similarly, the receiver-basedfeedback mechanism includes an upper band path and a lower band path. Inan embodiment, each of the upper band and lower band feedback pathsinclude an Automatic Gain Controller (AGC) (6306 and 6308), I/Qsample-and-hold (S/H) circuitry (6314, 6316 and 6318, 6320), switchingcircuitry (6322 and 6324), and optional interpolation filters (6326 and6328). In an embodiment, a switch 6330, controlled by the digitalcontrol module by means of input select signals 5810 and 5812, coupleseither the upper band or the lower band feedback paths to the digitalcontrol module. Further, based on the coupled feedback path, digitalcontrol module I/Qn Select signal 5808 controls switching circuitry 6322or 6324 to alternate the coupling of I data and Q data to the digitalcontrol module. Other implementations are also possible as can beunderstood by a person skilled in the art based on the teachings herein.

In an embodiment, the AGC circuitry is used to allow the receiver tofeedback useful I and Q information over a wide dynamic range of VPAoutput power. For example, output signals 5954, 5956, 5958, 5960, and5962 can vary from +35 dBm to −60 dBm in certain cell phoneapplications. For I and Q data to contain accurate feedback information,the I and Q output of the receiver needs to be scaled to utilize themajority of the input voltage range of the A/D in signal 5736,independently of the output signal power. Digital Control module 5800 isdesigned to control the VPA to the required output power, which allowsdigital control module 5800 to determine an appropriate receiver gain toachieve the proper A/D input voltage which is digitized through A/D5732.

A VPA analog core with a receiver-based feedback mechanism can beimplemented as a pure feedback, feedforward, or hybridfeedback/feedforward system. As described above, a pure feedbackimplementation requires a minimal amount of or no memory (RAM 5608,NVRAM 5610) in the digital control module. This may represent oneadvantage of an analog core implementation according to analog core6300, in addition to the elimination of differential feedbackmeasurement circuitry from the analog core. Nonetheless, analog core6300 can be programmed to operate as a pure feedback implementation bydisabling any feedforward correction in digital control module 5800, apure feedforward implementation by disabling the monitoring of feedbacksignals, or as a hybrid feedforward/feedback implementation withvariable feedforward/feedback utilization.

In an embodiment, the output stage of analog core 6300 includes optionaloutput stage protection circuitry. This is not shown in FIG. 63, but hasbeen described above with respect to analog core implementations 5900and 6100. Other aspects of analog core 6300 (bias control, power supply,etc.) are substantially similar to analog core 5900, and are describedabove with reference to FIG. 59.

FIG. 64 illustrates an output stage embodiment 6400 according to VPAanalog core implementation 6300. Output stage embodiment 6400 includes aMISO amplifier stage 6434 and an output switching stage. In anembodiment, MISO amplifier stage 6434 corresponds to MISO amplifier 5930and/or 5932, shown in FIG. 63 (that is, either or both of MISOamplifiers 5930, 5932 can be implemented using an amplifier such as MISOamplifier stage 6434).

Output stage embodiment 6400 is substantially similar to output stageembodiment 6000 illustrated in FIG. 60, with the main difference beingin the elimination of the differential branch measurement circuitry(6024 and 6026) due to the use a receiver-based feedback mechanism.

Similar to embodiment 6000, MISO amplifier stage 6434 in embodiment 6400includes a pre-driver amplification stage, embodied by Pre-Drivers 6406and 6408, a driver amplification stage, embodied by Drivers 6410 and6412, and a PA amplification stage, embodied by output stage PAs 6414and 6416. In an embodiment, constant envelope input signals MA IN1 6402and MA IN 6404 are amplified at each stage of MISO amplifier stage 6434,before being summed at the outputs of the PA stage of MISO amplifierstage 6434.

In an embodiment, MISO amplifier stage 6434 of output stage embodiment6400 is powered by power supply signals provided by voltage controlledpower supply circuits. In another embodiment, MISO amplifier stage 6434includes optional bias control circuitry controllable by the digitalcontrol module. In another embodiment, output stage embodiment 6400includes optional output stage protection circuitry (not shown in FIG.64). These aspects (power supply, bias control, and output protection)of output stage embodiment 6400 are substantially similar to what havebeen described above with respect to output stage embodiment 6000.

According to embodiments of the present invention, output stageembodiment 6400 may be fabricated using a SiGe (Silicon-Germanium)material including the MISO amplifier stage 6434, the output switchingstage 6420, and the optional output protection circuitry. In anotherembodiment, MISO amplifier stage 6434 is fabricated using SiGe, and theoutput switching stage 6420 is fabricated using GaAs. In anotherembodiment, the PA stage (PAs 6414 and 6416) of MISO amplifier stage6434 and the output switching stage 6420 are fabricated using GaAs,while other circuitry of MISO amplifier stage 6434 and optionalcircuitry of the output stage are fabricated using SiGe. In anotherembodiment, the PA stage, the driver stage (Drivers 6410 and 6412), andthe output switching stage 6420 are fabricated using GaAs, while othercircuitry of MISO amplifier stage 6434 and optional circuitry of theoutput stage are fabricated using SiGe. In another embodiment, the PAstage, the driver stage, the pre-driver stage (Pre-drivers 6406 and6408), and the output switching stage 6420 are fabricated using GaAs. Inanother embodiment, the VPA system may be implemented using CMOS for allcircuitry except for the output stage (6030 or 6032) which could beimplemented in SiGe or GaAs material. In another embodiment, the VPAsystem may be implemented in its entirety in CMOS. Other variationsand/or combinations of fabrication material(s) used for circuitry of theoutput stage are also possible, as can be understood by a person skilledin the art, and are therefore also within the scope of embodiments ofthe present invention. Further, output stages within the same the VPAmay be fabricated using different material, as illustrated in FIG. 61for example, where MISO amplifiers 6128, 6130, and 6134 are SiGeamplifiers and MISO amplifiers 6126 and 6132 are GaAs amplifiers (one ormore stages of their output stage are GaAs).

5. Real-Time Amplifier Class Control of VPA Output Stage

According to embodiments of the present invention, a VPA output stagecan be controlled to vary its amplifier class of operation according tochanges in its output waveform trajectory. This concept is illustratedin FIG. 65 with reference to an exemplary WCDMA waveform. The graph inFIG. 65 illustrates a timing diagram of a WCDMA output waveform envelopeversus the class of operation of the VPA output stage. Note that theoutput waveform envelope is directly proportional to the output power ofthe VPA output stage.

It is noted that the VPA output stage amplifier class traverses from aclass S amplifier to a class A amplifier as the output waveform envelopedecreases from its maximum value towards zero. At the zero crossing, theVPA output stage operates as a class A amplifier, before switching tohigher class amplifier operation as the output waveform envelopeincreases.

One important problem overcome by this real-time ability to control theVPA output stage amplifier class of operation is the phase accuracycontrol problem. With regard to the example shown in FIG. 65, the phaseaccuracy control problem lies in the fact that in order to produce highquality waveforms, at any given power level, a 40 dB of output powerdynamic range is desirable. However, the phase accuracy required toproduce a 40 dB output power dynamic range (around 1.14 degrees or 1.5picoseconds) is well beyond the tolerance of practical circuits in highvolume applications. As will be appreciated, the specific power rangescited in this paragraph, and elsewhere herein, are provided solely forillustrative purposes, and are not limiting.

Embodiments according to the present invention solve the phase accuracycontrol problem by transiting multiple classes of operation based onwaveform trajectory so as to maintain the best balance of efficiencyversus practical control accuracy for all waveforms. In embodiments, theoutput power dynamic range of the VPA output stage exceeds 90 dB.

In an embodiment, at higher instantaneous signal power levels, theamplifier class in operation (class S) is highly efficient and phaseaccuracy is easily achieved using phase control. At lower instantaneoussignal power levels, however, phase control may not be sufficient toachieve the required waveform linearity. This is illustrated in FIG. 66,which shows a plot of the VPA output power (in dBm) versus theoutphasing angle between branches of the VPA. It can be seen that athigh power levels, a change in outphasing angle results in a smalleroutput power change than at lower power levels. Accordingly, phasecontrol provides higher resolution power control at higher power levelsthan at lower power levels.

Accordingly, to support high resolution power control at lower powerlevels, other mechanisms of control are needed in addition to phasecontrol. FIG. 67 illustrates exemplary power control mechanismsaccording to embodiments of the present invention using an exemplaryQPSK waveform. The QPSK constellation is imposed on a unit circle in thecomplex domain defined by cos(wt) and sin(wt). The constellation spaceis partitioned between three concentric and non-intersecting regions: anoutermost “phase control only” region, a central “phase control, biascontrol, and amplitude control” region, and an innermost “bias controland amplitude control” region. According to embodiments of the presentinvention, the outermost, central, and innermost regions define the typeof power control to be applied according to the power level of theoutput waveform. For example, referring to FIG. 67, at lower powerlevels (points falling in the innermost region), bias control andamplitude control are used to provide the required waveform linearity.On the other hand, at higher power levels (points falling in theoutermost region), phase control (by controlling the outphasing angle)only is sufficient.

As can be understood by persons skilled in the art, the control regionsillustrated in FIG. 67 are provided for purposes of illustration onlyand are not limiting. Other control regions can be defined according toembodiments of the present invention. Typically, but not exclusively,the boundaries of the control regions are based on the ComplementaryCumulative Density Function (CCDF) of the desired output waveform andthe sideband performance criteria. Accordingly, the control regions'boundaries change according to the desired output waveform of the VPA.

In embodiments, the power control mechanisms defined by the differentcontrol regions enable the transition of the VPA output stage betweendifferent class amplifiers. This is shown in FIG. 68, which illustrates,side by side, the output stage amplifier class operation versus theoutput waveform envelope and the control regions imposed on a unitcircle. FIG. 69 further shows the output stage current in response tothe output waveform envelope. It is noted that the output stage currentclosely follows the output waveform envelope. In particular, it is notedthat the output stage current goes completely to zero when the outputwaveform envelope undergoes a zero crossing.

FIG. 70 illustrates the VPA output stage theoretical efficiency versusthe output stage current. Note that the output stage current waveform ofFIG. 70 corresponds to the one shown in FIG. 69. In an embodiment, theVPA output stage operates at 100% theoretical efficiency for 98% (orgreater) of the time. It is also noted from FIG. 70 the transition ofthe output stage between different amplifier classes of operationaccording to changes in the output stage current.

FIG. 71 illustrates an exemplary VPA according to an embodiment of thepresent invention. For illustrative purposes, and not purposes oflimitation, the exemplary embodiment of FIG. 71 will be used herein tofurther describe the various control mechanisms that can be used tocause the transitioning of the VPA output stage (illustrated as a MISOamplifier in FIG. 71) between different amplifier classes of operation.

The VPA embodiment of FIG. 71 includes a transfer function module, apair of vector modulators controlled by a frequency referencesynthesizer, and a MISO amplifier output stage. The transfer functionmodule receives I and Q data and generates amplitude information that isused by the vector modulators to generate substantially constantenvelope signals. The substantially constant envelope signals areamplified and summed in a single operation using the MISO amplifieroutput stage.

According to embodiments of the present invention, the MISO amplifieroutput stage can be caused to transition in real time between differentamplifier classes of operation according to changes in output waveformtrajectory. In an embodiment, this is achieved by controlling the phasesof the constant envelope signals generated by the vector modulators. Inanother embodiment, amplitudes of the MISO amplifier input signals arecontrolled using the transfer function. In another embodiment, the MISOamplifier inputs are biased (biasing of the MISO inputs can be done atany amplification stage within the MISO amplifier) using the transferfunction to control the MISO amplifier class of operation. In otherembodiments, combinations of these control mechanisms (phase, input biasand/or input amplitude) are used to enable the MISO amplifier stage totransition between different amplifier classes of operation.

FIG. 72 is a process flowchart 100 that illustrates a method forreal-time amplifier class control in a power amplifier, according tochanges in output waveform trajectory, according to an embodiment of theinvention. Process flowchart 100 begins in step 110, which includesdetermining an instantaneous power level of a desired output waveform.In an embodiment, the instantaneous power level is determined as afunction of the desired output waveform envelope.

Based on the determined instantaneous power level, step 120 of processflowchart 100 includes determining a desired amplifier class ofoperation, wherein said amplifier class of operation optimizes the powerefficiency and linearity of the power amplifier. In an embodiment,determining the amplifier class of operation depends on the specifictype of desired output waveform (e.g., CDMA, GSM, EDGE).

Step 130 includes controlling the power amplifier to operate accordingto the determined amplifier class of operation. In an embodiment, thepower amplifier is controlled using phase control, bias control, and/oramplitude control methods, as described herein.

According to process flowchart 100, the power amplifier is controlledsuch that it transitions between different amplifier classes ofoperation according to the instantaneous power level of the desiredoutput waveform. In other embodiments, the power amplifier is controlledsuch that it transitions between different amplifier classes ofoperation according the average output power of the desired outputwaveform. In further embodiments, the power amplifier is controlled suchthat it transitions between different amplifier classes of operationaccording to both the instantaneous power level and the average outputpower of the desired output waveform.

According to embodiments of the present invention, the power amplifiercan be controlled to transition from a class A amplifier to a class Samplifier, while passing through intermediary amplifier classes (AB, B,C, and D).

Embodiments of the invention control transitioning of the poweramplifier(s) to different amplifier classes as follows:

To achieve a class A amplifier, the drive level and bias of the poweramplifier are controlled so that the output current conduction angle isequal to 360 degrees. The conduction angle is defined as the angularportion of a drive cycle in which output current is flowing through theamplifier.

To achieve a class AB amplifier, the drive level and bias of the poweramplifier are controlled so that the output current conduction angle isgreater than 180 degrees and less than 360 degrees.

To achieve a class B amplifier, the drive level and bias of the poweramplifier are controlled so that the output current conduction angle isapproximately equal to 180 degrees.

To achieve a class C amplifier, the drive level and bias of the poweramplifier are controlled so that the output current conduction angle isless than 180 degrees.

To achieve a class D amplifier, the drive level and bias of the poweramplifier are controlled so that the amplifier is operated in switchmode (on/off).

To achieve a class S amplifier, the amplifier is controlled to generatea Pulse Width Modulated (PWM) output signal.

In an embodiment, the above described real-time amplifier class controlof the VPA output stage is accompanied by a dynamic change in thetransfer function being implemented in the digital control module of theVPA. This is further described below with respect to FIGS. 73-77.

FIG. 73 illustrates an example VPA output stage according to an npnimplementation with two branches. Each branch of the VPA output stagereceives a respective substantially constant envelope signal. Thesubstantially constant envelope signals are illustrated as IN1 and IN2in FIG. 73. Transistors of the VPA output stage are coupled together bytheir emitter nodes to form an output node of the VPA.

When the VPA output stage operates as a class S amplifier, iteffectuates Pulse Width Modulation (PWM) on the received substantiallyconstant envelope signals IN1 and IN2. A theoretical equivalent circuitof the VPA output stage in this amplifier class of operation isillustrated in FIG. 74. Note that transistors of the VPA output stageare equivalent to switching amplifiers in this class of operation. Theoutput of the VPA as a function of the outphasing angle θ between thesubstantially constant envelope signals IN1 and IN2 (assuming that IN1and IN2 have substantially equal amplitude of value A) is given by

${{SQ}(\theta)} = {A{\frac{\pi - \theta}{2\pi}.}}$

A plot of this function, described previously as the magnitude to phaseshift transform, is illustrated in FIG. 76.

On the other hand, when the VPA output stage operates as a class Aamplifier, it emulates a perfect summing node. A theoretical equivalentcircuit of the VPA output stage in this amplifier class of operation isillustrated in FIG. 75. Note that transistors of the VPA output stageare equivalent to current sources in this class of operation. The outputof the VPA as function of the outphasing angle θ between thesubstantially constant envelope signals IN1 and IN2 (assuming that IN1and IN2 have substantially equal amplitude of value A) is given byR(θ)=AA√{square root over (2(1 cos(θ)))}. A plot of this function,described previously as the magnitude to phase shift transform, isillustrated in FIG. 76.

According to an embodiment of the present invention, amplifier classesof operation A and S represent two extremes of the amplifier operatingrange of the VPA output stage. However, as described above, the VPAoutput stage may transition a plurality of other amplifier classes ofoperation including, for example, classes AB, B, C, and D. Accordingly,the transfer function implemented by the digital control module of theVPA varies within a spectrum of magnitude to phase shift transformfunctions, with the transform functions illustrated in FIG. 76representing the boundaries of this spectrum. This is shown in FIG. 77,which illustrates a spectrum of magnitude to phase shift transformfunctions corresponding to a range of amplifier classes of operation ofthe VPA output stage. FIG. 77 illustrates 6 functions corresponding tothe six amplifier classes of operation A, AB, B, C, D, and S. Ingeneral, however, an infinite number of functions can be generated usingthe functions corresponding to the two extreme classes of operation Aand S. In an embodiment, this is performed using a weighted sum of thetwo functions and is given by (1−K)×R(θ)+K×SQ(θ), with 0≦K≦1.

6. Additional MISO Design Concepts 6.1) Implementing Boolean LogicFunctions Using MISO Power Amplifiers

In FIGS. 51D-F described above, various MISO power amplifier (PA)embodiments have been provided. In particular, various embodiments havebeen provided to illustrate how, for example, a two-input single-outputPA can be used as a building block to create multiple-inputsingle-output PAs. Further, various npn, pnp, complementary npn-pnp,NMOS, PMOS, and complementary NMOS-PMOS implementations were described.In this section, additional MISO design concepts are provided. Inparticular, these concepts illustrate how a MISO PA can be designed tooperate in switching mode as a digital logic function, including forexample a NOR, OR, NAND, or AND logic function, depending on the systemrequirements of the particular implementation/apparatus using the MISOPA. Implementation of other logic functions will be apparent to personsskilled in the art based on the teachings provided herein.

As described above, in embodiments, MISO PAs provide simultaneousamplification and combination of two or more phase varying substantiallyconstant envelope signals. In certain modes of operation, the MISOtransistors are biased into a non-linear switch mode. In such mode, theMISO PA provides a basic logic function, which can be described usingBoolean algebra, in addition to simultaneous amplification andcombination of signals. This additional functionality of MISO PAs isfurther described below.

FIG. 79 illustrates an example MISO power amplifier configuration 7900,which can be operated as a Boolean NOR function according to anembodiment of the present invention. As shown in FIG. 79, MISOconfiguration 7900 includes two collector-coupled NPN transistors 7902and 7904. Inputs IN1 and IN2 are provided respectively by the baseterminals of transistors 7902 and 7904. The output terminal of MISOconfiguration 7900 is provided by the common collector node oftransistors 7902 and 7904. Typically, a pull-up impedance (not shown inFIG. 79) couples the common collector node of transistors 7902 and 7904to a power supply. As would be understood by a person skilled in the artbased on the teachings herein, MISO configuration 7900 can beequivalently implemented using other types of transistors, including forexample PNP, NMOS, or PMOS transistors.

According to an embodiment of the present invention, MISO configuration7900 can be operated to perform a digital NOR gate function. This can bedone by driving inputs IN1 and IN2 using pulse-width modulated (PWM)signals, thereby causing MISO transistors 7902 and 7904 to operate inswitch mode or class S mode of operation. For example, assuming thatinputs IN1 and IN2 are both driven by square waveforms that alternatebetween a low voltage value (e.g., 0 volts) and a high voltage value(e.g., 5 volts), then the output of MISO configuration 7900 will takethe low voltage value when either IN1 or IN2 takes the high voltagevalue and will take the high voltage value when both IN1 and IN2 takethe low voltage value. More generally, the output of MISO configuration7900 will be a logic low when either of IN1 and IN2 is a logic high anda logic high when both IN1 and IN2 are a logic low. This is equivalentto a NOR function which logic table is illustrated by table 7906 of FIG.79.

FIG. 80 illustrates an example MISO power amplifier configuration 8000,which can be operated as a Boolean OR function according to anembodiment of the present invention. As shown in FIG. 80, MISOconfiguration 8000 includes two emitter-coupled NPN transistors 8002 and8004. Inputs IN1 and IN2 are provided respectively by the base terminalsof transistors 8002 and 8004. The output terminal of MISO configuration8000 is provided by the common emitter node of transistors 8002 and8004. Typically, a pull-down impedance (not shown in FIG. 80) couplesthe common emitter node of transistors 8002 and 8004 to ground. As wouldbe understood by a person skilled in the art based on the teachingsherein, MISO configuration 8000 can be equivalently implemented usingother types of transistors, including for example PNP, NMOS, or PMOStransistors.

According to an embodiment of the present invention, MISO configuration8000 can be operated to perform a digital OR gate function. This can bedone by driving inputs IN1 and IN2 using PWM signals, thereby causingMISO transistors 8002 and 8004 to operate in switch mode or class S modeof operation. For example, assuming that inputs IN1 and IN2 are bothdriven by square waveforms that alternate between a low voltage value(e.g., 0 volts) and a high voltage value (e.g., 5 volts), then theoutput of MISO configuration 8000 will take the low voltage value whenboth IN1 and IN2 take the low voltage value and will take the highvoltage value when either IN1 or IN2 take the high voltage value. Moregenerally, the output of MISO configuration 8000 will be a logic lowwhen both IN1 and IN2 are a logic low and a logic high when either IN1or IN2 is a logic high. This is equivalent to an OR function which logictable is illustrated by table 8006 of FIG. 80.

FIG. 81 illustrates an example MISO power amplifier configuration 8100,which can be operated as a Boolean NAND function according to anembodiment of the present invention. As shown in FIG. 81, MISOconfiguration 8100 includes two collector-coupled NPN transistors 8102and 8106 and two emitter-coupled transistors 8104 and 8108. Further, theemitters of transistors 8102 and 8106 are respectively coupled to thecollectors of transistors 8104 and 8108. In addition, transistors 8102and 8104 have common base terminals with transistors 8108 and 8106,respectively. Inputs IN1 and IN2 are provided respectively by the baseterminals of transistors 8102/8108 and 8104/8106. The output terminal ofMISO configuration 8100 is provided by the common collector node oftransistors 8102 and 8106. Typically, a pull-up impedance (not shown inFIG. 81) couples the common collector node of transistors 8102 and 8106to a power supply. As would be understood by a person skilled in the artbased on the teachings herein, MISO configuration 8100 can beequivalently implemented using other types of transistors, including forexample PNP, NMOS, or PMOS transistors.

According to an embodiment of the present invention, MISO configuration8100 can be operated to perform a digital NAND gate function. This canbe done by driving inputs IN1 and IN2 using PWM signals, thereby causingMISO transistors 8102, 8104, 8106, and 8108 to operate in switch mode orclass S mode of operation. For example, assuming that inputs IN1 and IN2are both driven by square waveforms that alternate between a low voltagevalue (e.g., 0 volts) and a high voltage value (e.g., 5 volts), then theoutput of MISO configuration 8100 will take the low voltage value whenboth IN1 and IN2 take the high voltage value and will take the highvoltage value when either IN1 or IN2 take the low voltage value. Moregenerally, the output of MISO configuration 8100 will be a logic lowwhen both IN1 and IN2 are a logic high and a logic high when either IN1or IN2 is a logic low. This is equivalent to an NAND function whichlogic table is illustrated by table 8110 of FIG. 81.

FIG. 82 illustrates an example MISO power amplifier configuration 8200,which can be operated as a Boolean AND function according to anembodiment of the present invention. As shown in FIG. 82, MISOconfiguration 8200 includes two collector-coupled NPN transistors 8202and 8206 and two emitter-coupled transistors 8204 and 8208. Further, theemitters of transistors 8202 and 8206 are respectively coupled to thecollectors of transistors 8204 and 8208. In addition, transistors 8202and 8204 have common base terminals with transistors 8208 and 8206,respectively. Inputs IN1 and IN2 are provided respectively by the baseterminals of transistors 8202/8208 and 8204/8206. The output terminal ofMISO configuration 8200 is provided by the common emitter node oftransistors 8204 and 8208. Typically, a pull-down impedance (not shownin FIG. 82) couples the common emitter node of transistors 8204 and 8208to ground. As would be understood by a person skilled in the art basedon the teachings herein, MISO configuration 8100 can be equivalentlyimplemented using other types of transistors, including for example PNP,NMOS, or PMOS transistors.

According to an embodiment of the present invention, MISO configuration8200 can be operated to perform a digital AND gate function. This can bedone by driving inputs IN1 and IN2 using PWM signals, thereby causingMISO transistors 8202, 8204, 8206, and 8208 to operate in switch mode orclass S mode of operation. For example, assuming that inputs IN1 and IN2are both driven by square waveforms that alternate between a low voltagevalue (e.g., 0 volts) and a high voltage value (e.g., 5 volts), then theoutput of MISO configuration 8200 will take the low voltage value wheneither IN1 or IN2 takes the low voltage value and will take the highvoltage value when both IN1 and IN2 take the high voltage value. Moregenerally, the output of MISO configuration 8200 will be a logic lowwhen either IN1 or IN2 is a logic low and a logic high when both IN1 andIN2 are a logic high. This is equivalent to an AND function which logictable is illustrated by table 8210 of FIG. 82.

FIGS. 79-83 above show how different MISO power amplifier configurationscan be used to perform basic Boolean logic functions, including forexample, NOR, OR, NAND, and AND functions. In addition, as describedabove, the different MISO configurations can be used to perform poweramplification functions, including simultaneous amplification andcombination of two or more phase varying substantially constant envelopesignals to generate a desired RF output signal. However, while thedifferent MISO configurations perform similar RF output signalgeneration and power amplification functions, they may have differentoperation characteristics. This is further explored below with referenceto FIGS. 83-91, which illustrate a comparison between MISO configuration7900 which performs a NOR function and MISO configuration 8100 thatperforms a NAND function.

FIG. 83 illustrates an example simulation test bench 8300 of MISO poweramplifier configuration 7900 according to an embodiment of the presentinvention.

For ease of illustration, example test bench 8300 uses switches to modelMISO transistors 7902 and 7904. For example, switch 8302 may correspondto MISO transistor 7902 of MISO configuration 7900. Similarly, switch8304 may correspond to MISO transistor 7904 of MISO configuration 7900.Accordingly, input terminals 8306 and 8308 of test bench 8300 correspondrespectively to inputs IN1 and IN2 of MISO configuration 7900.

As described above, the common collector node of MISO transistors 7902and 7904 is coupled to a power supply via a pull-up impedance. In testbench 8300, this is modeled using a pull-up resistor 8318 and a 3V DCpower supply 8310. A current probe 8320 is also coupled between powersupply 8310 and resistor 8318 to measure the output current of the MISOconfiguration.

Node 8312 provides the output terminal of the MISO configurationsimulated in test bench 8300. Accordingly, node 8312 corresponds to theoutput terminal of MISO configuration 7900. Further, when inputterminals 8306 and 8308 are driven by PWM input signals, the waveform atnode 8312 is a two-level PWM signal that relates to the input signalsaccording to NOR logic table 7906 of FIG. 79.

In an embodiment, when MISO configuration 7900 is used to perform poweramplification functions in addition to performing a digital NORfunction, the PWM output signal of MISO configuration 7900 can be inputinto an optional bandpass filter to generate a continuous multi-levelwaveform output. The bandpass filter filters the pulses of the input PWMsignal to generate analog values proportional thereto. In test bench8300, this is modeled using bandpass filter 8314, which receives theoutput 8312 of the simulated MISO configuration and generates RF outputsignal 8316. RF output signal 8316 is a power amplified signal whichresults from the simultaneous amplification and combination of the inputsignals driving input terminals 8306 and 8308.

FIG. 84 illustrates an example simulation test bench 8400 of MISO poweramplifier configuration 8100 according to an embodiment of the presentinvention.

For ease of illustration, example test bench 8400 uses switches to modelMISO transistors 8102, 8104, 8106, and 8108. For example, switches 8402,8404, 8406, and 8408 in test bench 8400 may correspond respectively toMISO transistors 8102, 8104, 8106, and 8108 of MISO configuration 8100.Accordingly, input terminals 8410 and 8412 of test bench 8400 correspondrespectively to inputs IN1 and IN2 of MISO configuration 8100.

As described above, the common collector node of MISO transistors 8102and 8106 is coupled to a power supply via a pull-up impedance. In testbench 8400, this is modeled using a pull-up resistor 8418 and a 3V DCpower supply 8414. A current probe 8416 is also coupled between powersupply 8414 and resistor 8418 to measure the output current of the MISOconfiguration.

Node 8420 provides the output terminal of the MISO configurationsimulated in test bench 8400. Accordingly, node 8420 corresponds to theoutput terminal of MISO configuration 8100. Further, when inputterminals 8410 and 8412 are driven by PWM input signals, the waveform atnode 8420 is a two-level PWM signal that relates to the input signalsaccording to NAND logic table 8110 of FIG. 81.

In an embodiment, when MISO configuration 8100 is used to perform poweramplification functions in addition to performing a digital NANDfunction, the PWM output signal of MISO configuration 8100 can be inputinto an optional bandpass filter to generate a continuous multi-levelwaveform output. The bandpass filter filters the pulses of the input PWMsignal to generate analog values proportional thereto. In test bench8400, this is modeled using bandpass filter 8422, which receives theoutput 8420 of the simulated MISO configuration and generates RF outputsignal 8424. In an embodiment, RF output signal 8424 is a poweramplified signal which results from the simultaneous amplification andcombination of the input signals driving input terminals 8410 and 8412.

FIGS. 85-87 to be described below illustrate that MISO configurationembodiments 7900 and 8100, while performing different Boolean logicfunctions in class S mode, perform substantially similar amplificationfunctions when provided the same driving input signals. For the purposeof this comparison, it is not necessary that the MISO configurations areoperated in class S mode, although the comparison may be done with theMISO configurations operated in class S mode.

FIG. 85 illustrates example upper branch and lower branch input signalsprovided to the MISO power amplifier configuration simulated in testbench 8300. In particular, the waveform shown in red corresponds to theupper branch input signal, and the waveform shown in blue corresponds tothe lower branch input signal. As shown in FIG. 85, the upper branch andlower branch input signals are substantially constant envelope sine wavesignals which vary in phase from 0 to 180 degrees relative to eachother.

Note that to operate the MISO configuration in class S mode, the upperbranch and lower branch input signals need to be two-level PWM signals.Such signals can be generated from the sine waveforms shown in FIG. 85by passing the sine waveforms through a bandpass modulator (e.g.,Delta-Sigma Modulator) followed by a pre-amplifier to generatecontinuous-time PWM signals.

FIG. 86 illustrates example upper branch and lower branch input signalsprovided to the MISO power amplifier configuration simulated in testbench 8400. In particular, the waveform shown in red corresponds to theupper branch input signal, and the waveform shown in blue corresponds tothe lower branch input signal. As shown in FIG. 86, the upper branch andlower branch input signals are substantially constant envelope sine wavesignals which vary in phase from 0 to 180 degrees relative to eachother.

Note that the upper branch and lower branch input signals shown in FIG.85 are substantially similar to the upper branch and lower branch inputsignals shown in FIG. 86. However, the two sets of waveforms are shownat different zoom levels in FIGS. 85 and 86.

FIG. 87 illustrates example output waveforms generated by the MISO poweramplifier configurations simulated in test benches 8300 and 8400. Inparticular, waveform 8702 is the RF output of the MISO configurationsimulated in test bench 8400 in response to the input signals shown inFIG. 86. Waveform 8704 is the RF output of the MISO configurationsimulated in test bench 8300 in response to the input signals shown inFIG. 85.

As noted above, the two example MISO configurations perform differentBoolean functions in class S mode. However, as can be seen from FIG. 87,the two MISO configurations have substantially similar RF outputwaveforms in response to substantially similar input signals.Accordingly, the two MISO configurations perform substantially similarRF output signal generation and power amplification functions, but canbe operated to perform different Boolean logic functions. This, as wouldbe understood by a person skilled in the art based on the teachingsherein, applies not only to a NOR MISO configuration and a NAND MISOconfiguration, but to any two different MISO configurations as describedabove. For example, an OR MISO configuration and an AND MISOconfiguration also perform substantially similar RF output signalgeneration and power amplification functions but different Boolean logicfunctions.

Nonetheless, any two MISO configurations as described above, whileperforming substantially similar RF output signal generation and poweramplification functions, have different operation characteristics. Thesecharacteristics, depending on the implementation and/or systemrequirements, can be an important factor to consider in deciding whichMISO configuration to employ in a particular system design. This isfurther explored in FIGS. 88-91, which illustrate that while MISOconfigurations 7900 and 8100 perform substantially similar RF outputsignal generation and power amplification functions, they have differentoperation characteristics, including different output powercapabilities, output current, and efficiency characteristics.

FIG. 88 illustrates example plots of power output versus outphasingangle for the MISO power amplifier configurations simulated in FIGS. 83and 84. In particular, curves 8802 and 8804 represent respectively thenormalized equivalent power output versus the outphasing angle (i.e.,phase shift angle between the input signals driving the MISOconfiguration) for the NOR MISO configuration simulated in test bench8300 and the NAND MISO configuration simulated in test bench 8400.

As shown in FIG. 88, the NAND MISO configuration has slightly less poweroutput than the NOR MISO configuration for a given outphasing anglevalue. This is due to the fact that a NAND MISO configuration (e.g.,MISO configuration 8100) has two transistors in series between the RFoutput and ground compared to a single transistor between the RF outputand ground in a NOR MISO configuration (e.g., MISO configuration 7900),which results in lower output voltage in the NAND MISO configurationassuming equal voltage power supplies are used for both configurations.

Note, however, that, apart from the NAND MISO configuration havingslightly lower power output than the NOR MISO configuration, the twoconfigurations have substantially similar power output transferfunctions versus the outphasing angle. Indeed, as shown in FIG. 88,curves 8802 and 8804 appear to have substantially similar shapes, albeitcurve 8804 is slightly lower than curve 8802. Further, note that despitehaving slightly different power outputs, the NOR MISO configuration andthe NAND MISO configuration generate, given same inputs, substantiallysimilar RF output waveforms as described above.

However, the NOR MISO configuration and the NAND MISO configuration havedifferent output current characteristics, which result in differentpower efficiency characteristics. This makes the two configurationssuitable for different implementations and/or system requirements. Thisis further explored below with reference to FIGS. 89-91.

FIG. 89 illustrates example plots of output current versus outphasingangle for the MISO power amplifier configurations simulated in FIGS. 83and 84. In particular, curves 8902 and 8904 represent respectively themean output current versus the outphasing angle (i.e., phase shift anglebetween the input signals driving the MISO configuration) for the NORMISO configuration simulated in test bench 8300 and the NAND MISOconfiguration simulated in test bench 8400. Note that the output currentherein refers to the current that passes through the output node of theMISO configuration.

As shown in FIG. 89, although the NOR MISO and the NAND MISOconfigurations generate substantially similar output responses, theiroutput current characteristics are significantly different due to theirdifferent circuit topologies. Indeed, as shown by curve 8902, the outputcurrent of the NOR MISO configuration increases with increases inoutphasing angle. In contrast, the output current of the NAND MISOconfiguration decreases with increases in outphasing angle.

For the NOR MISO configuration, the output current behavior shown inFIG. 89 is explained as follows. At 0 degrees of outphasing angle, theclass S output of the MISO configuration is a PWM signal with 50% dutycycle. When the outphasing angle is increased, the class S outputbecomes a PWM signal with shorter width pulses, with the output reaching0% duty cycle at 180 degrees of outphasing angle. However, while theduty cycle decreases with increasing outphasing angle, the output nodeis more frequently being coupled to ground, drawing more current fromthe power supply. For example, at 0% duty cycle, the input signals intothe NOR MISO configuration are 180 degrees out of phase relative to eachother. Referring to NOR MISO configuration 7900, for example, this meansthat at any time at least one of transistors 7902 and 7904 is ON,coupling the output node to ground. As such, while the output of theMISO configuration is zero, the MISO configuration is drawing maximumcurrent from the power supply. As described above, according to anembodiment of the present invention, such scenario can be avoided byusing bias and/or control signals to prevent the MISO amplifier fromdrawing current when the output is zero.

For the NAND MISO configuration, the exact opposite of what is describedabove for the NOR MISO configuration occurs. In other words, when theoutphasing angle is increased, the class S output becomes a PWM signalwith larger width pulses, with the output reaching 100% duty cycle at180 degrees of outphasing. However, as the duty cycle increases withincreasing outphasing angle, the output node is less frequently beingcoupled to ground, drawing less current from the power supply. Forexample, at 100% duty cycle, the input signals into the NAND MISOconfiguration are 180 degrees out of phase relative to each other.Referring to NAND MISO configuration 8100, for example, this means thatat any time at least one of transistors 8102 and 8104 is OFF and atleast one of transistors 8106 and 8108 is OFF. Accordingly, the outputnode of MISO configuration 8100 can never be coupled to ground at 180degrees of outphasing, resulting in zero output current being drawn fromthe power supply as shown by curve 8904.

For further illustration, FIG. 90 illustrates example plots of poweroutput and output current versus outphasing angle for the MISO poweramplifiers simulated in FIGS. 83 and 84. In particular, plot 9002 showsthe power output (curve 9004) and the output current (curve 9006) versusthe outphasing angle for the NAND MISO configuration simulated in testbench 8400. Similarly, plot 9004 shows the power output (curve 9010) andthe output current (curve 9012) versus the outphasing angle for the NORMISO configuration simulated in test bench 8300. As shown in plot 9002,the power output varies in the same direction as the output current inthe NAND MISO configuration with changes in outphasing angle. Incontrast, as shown in plot 9008, the power output varies in oppositedirection as the output current in the NOR MISO configuration withchanges in outphasing angle.

Circuit topology differences between the NOR MISO and the NAND MISOconfigurations extend not only to output current characteristics butalso to power efficiency characteristics. FIG. 91 illustrates exampleplots of normalized efficiency versus outphasing angle for the MISOpower amplifiers simulated in FIGS. 83 and 84. In particular, curve 9102represents the normalized efficiency curve versus the outphasing anglefor the NAND MISO configuration simulated in test bench 8400. Curve 9104represents the normalized efficiency versus the outphasing angle for theNOR MISO configuration simulated in test bench 8300.

As shown in FIG. 91, curves 9102 and 9104 intersect at 0 degrees ofoutphasing angle, which indicates that at 0 degrees of outphasing theNAND MISO configuration and the NOR MISO configuration have equal powerefficiency. This is illustrated by marker “m1” in FIG. 91, which showsthat at 0 degrees of outphasing, the efficiency of either configurationis approximately 71%.

When the outphasing angle increases, however, the efficiency of the NORMISO configuration begins to drop immediately. In contrast, theefficiency of the NAND MISO configuration increases between 0 and ˜25degrees of outphasing angle, before starting to drop with furtherincreases of outphasing angle. Throughout the outphasing angle range,however, the efficiency of the NAND MISO configuration remainsconsiderably higher than the efficiency of the NOR MISO configuration.For example, as illustrated by markers “m2” and “m3” in FIG. 91, at 55degrees of outphasing, the efficiency of the NAND MISO configuration isapproximately 57%, whereas the efficiency of the NOR MISO configurationis approximately 15%.

It is noted that in the above, it is assumed that the MISOconfigurations are operated without any additional bias and/or controlsignals, which, as described in previous sections, may be used to affectthe output current and/or the power efficiency of a MISO configuration.

Accordingly, in the above, different MISO power amplifier configurationshave been described. The different MISO configurations can be operatedto perform different Boolean logic functions. At the same time, thedifferent MISO configurations have substantially similar RF outputsignal generation and power amplification functions, includingsubstantially similar output power transfer functions versus theoutphasing angle. Yet, the different MISO configurations can havedifferent output current and/or power efficiency characteristics.

As such, depending on the implementation and/or system requirements,different

MISO configurations may be selected. Such requirements may include, forexample, power supply requirements, output power requirements, availablebias control functions, the amount of time spent in switch modeoperation, the type of transistors (e.g., NPN, PNP, nFET, pFET, pHEMT,MOSFET, MESFET, CMOS, etc.) available, and the available functionaldomains such as digital, analog, or both. For example, when power supplyrequirements are stringent and a large output power dynamic range isdesired, a NOR MISO configuration may be more suitable than a NAND MISOconfiguration. In contrast, when power efficiency is a concern and nobias control functions are available, a NAND MISO configuration may bebetter to use than a NOR MISO configuration.

6.2) Combined Polar-VPA Architectures

In this section, example combined polar-VPA architectures are provided.These architectures illustrate how VPAs according to embodiments of thepresent invention can be combined with polar architecture amplifiers tocreate additional functionality. For example, a polar amplifier designthat supports certain output waveforms may be supplemented with a VPA tosupport additional waveforms that the VPA supports.

According to embodiments of the present invention, combined polar-VPAarchitectures can be operated in polar, polar plus VPA, or VPA onlymode. In an embodiment, the operational mode selected for a combinedpolar-VPA architecture may be based on but not limited to the requiredoutput waveforms (e.g., GSM, EDGE, W-CDMA, CDMA 2000, HSUPA, HSDPA,OFDM, WiMax, or WiBro). The combination approach may also be selectedbased on calibration requirements and/or production testingrequirements.

FIG. 92 illustrates an example combined polar-VPA architecture 9200according to an embodiment of the present invention. As shown in FIG.92, the combined polar-VPA architecture 9200 includes a polar component9202 and a VPA component 9204. As described above, the VPA component9204 includes such elements as vector modulators, interpolation filters,pre-drivers, drivers, and MISO power amplifiers. Further, VPA component9204 may receive bias and/or control signals as described in previoussections above.

In an embodiment, the VPA may also receive a digitally controller powersupply (DCPS) signal or a switching modulated power supply (SMPS)signal, which can be used to control the amplitude of the output signalgenerated by the VPA. Note that the bandwidth of the DCPS or SMPS in apolar design without a VPA must be greater than the output signalbandwidth in order to reproduce the amplitude component of the outputsignal correctly. This increased high current power supply bandwidthdirectly affects the in-band and out-of-band noise performance of thesystem, the overall efficiency of the system, and the sideband orACPR/ACLR (Adjacent Channel Power Ratio/Adjacent Channel Leakage Ratio)performance of the system.

Fortunately, in other embodiments, because the VPA can control both thephase and the amplitude of the output using substantially constantenvelope signals, the DCPS or the SMPS can be eliminated. Note thateliminating the DCPS or SMPS and relying instead on VPA controls togenerate the correct output signal amplitude has two main advantages.First, a polar-VPA architecture has the advantage of not requiring timealignment between the amplitude and phase signal paths as is required inpolar only designs. Second, using a VPA in combination with a polardesign eliminates the need for high DCPS or SMPS bandwidths, whichenables the combination architecture to be used in more applications.

FIG. 93 illustrates another example combined polar-VPA architecture 9300according to an embodiment of the present invention. Combined polar-VPAarchitecture 9300 includes a polar component 9302 and a VPA component9304. VPA component 9304 includes such elements as vector modulators,interpolation filters, pre-drivers, drivers, and MISO power amplifiers.In addition, VPA component 9304 receives various bias and/or controlsignals, which create several control layers for controlling the phaseand amplitude of the VPA. As such, the DCPS signal in architecture 9300can be eliminated as described above.

According to embodiments of the present invention, various controls canbe used to achieve a require range of amplitude control withoutcontrolling the supply voltage to the MISO amplifier (i.e., eliminatingthe DCPS or SMPS supplies). In an embodiment, amplitude control isachieved by controlling the vector modulators of the VPA componentand/or by controlling the bias of the MISO amplifier. In anotherembodiment, amplitude control is performed by controlling the vectormodulators, the MISO bias, and/or the MISO input gain control. In afurther embodiment, amplitude control is performed by controlling thevector modulators, the MISO bias, the MISO input gain control, and/or byMISO input pulse density modulation (PDM). The latter type of control isillustrated in FIG. 94, which shows an example VPA component 9400, whichcan be used in a combined polar-VPA architecture according to anembodiment of the present invention.

VPA component 9400 includes such elements as vectors modulators,interpolation filters, pre-drivers, drivers, and MISO power amplifiers.In addition, as shown in FIG. 94, VPA component 9400 includes a pair ofpulse density modulators 9402 and 9404. Pulse density modulators 9402and 9404 are coupled between the vector modulator and the amplificationstages in the upper and lower branches of the VPA, respectively. In anembodiment, pulse density modulators 9402 and 9404 receive a pulsedensity control signal 9406 and perform PDM on the outputs of the vectormodulators according to pulse density control signal 9406 to vary theamplitude of the output signal of the MISO amplifier.

7. SUMMARY

Mathematical basis for a new concept related to processing signals toprovide power amplification and up-conversion is provided herein. Thesenew concepts permit arbitrary waveforms to be constructed from sums ofwaveforms which are substantially constant envelope in nature. Desiredoutput signals and waveforms may be constructed from substantiallyconstant envelope constituent signals which can be created from theknowledge of the complex envelope of the desired output signal.Constituent signals are summed using new, unique, and novel techniquesnot available commercially, not taught or found in literature or relatedart. Furthermore, the blend of various techniques and circuits providedin the disclosure provide unique aspects of the invention which permitssuperior linearity, power added efficiency, monolithic implementationand low cost when compared to current offerings. In addition,embodiments of the invention are inherently less sensitive to processand temperature variations. Certain embodiments include the use ofmultiple input single output amplifiers described herein.

Embodiments of the invention can be implemented by a blend of hardware,software and firmware. Both digital and analog techniques can be usedwith or without microprocessors and DSP's.

Embodiments of the invention can be implemented for communicationssystems and electronics in general. In addition, and without limitation,mechanics, electro mechanics, electro optics, and fluid mechanics canmake use of the same principles for efficiently amplifying andtransducing signals.

8. Conclusion

The present invention has been described above with the aid offunctional building blocks illustrating the performance of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have been arbitrarily defined herein for the convenienceof the description. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed. Any such alternate boundaries are thus within the scope andspirit of the claimed invention. One skilled in the art will recognizethat these functional building blocks can be implemented by discretecomponents, application specific integrated circuits, processorsexecuting appropriate software and the like and combinations thereof

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. Thus, the breadth and scope of thepresent invention should not be limited by any of the above-describedexemplary embodiments, but should be defined only in accordance with thefollowing claims and their equivalents.

What is claimed is:
 1. A method of controlling an amplifier, comprising:determining a power level of an output waveform; determining a desiredamplifier class of operation according to the determined power level;and controlling the amplifier to operate according to the desired classof operation.
 2. The method of claim 1, wherein determining a powerlevel comprises determining an instantaneous power level as a functionof a desired output waveform envelope.
 3. The method of claim 1, furthercomprising controlling the power amplifier to operate according to a newclass of operation.
 4. The method of claim 3, wherein controlling thepower amplifier to operate according to a new class of operationcomprises transitioning the power amplifier through an intermediaryclass.
 5. The method of claim 1, further comprising: determining theinstantaneous power level of the desired output waveform; andcontrolling the power amplifier to operate in according to a new classof operation based on the instantaneous power level.
 6. The method ofclaim 1, further comprising: determining an average output power of thedesired output waveform; and controlling the power amplifier to operateaccording to a new class of operation based on the average output power.7. The method of claim 1, further comprising: determining theinstantaneous power level of the desired output waveform determining anaverage output power of the desired output waveform; and controlling thepower amplifier to operate according to a new class of operation basedon the instantaneous power level and average output power.
 8. The methodof claim 1, wherein controlling the power amplifier comprisescontrolling a drive level and a bias of the amplifier so that an outputcurrent conduction angle reaches a predetermined level based on thedesired class of operation.
 9. The method of claim 1, whereincontrolling the amplifier comprise generating a pulse width modulatedoutput signal.
 10. The method of claim 1, wherein controlling theamplifier comprises operating the amplifier in a switch mode.
 11. Anapparatus, comprising: an amplifier; and an amplifier controllerconfigured to: determine a power level of an output waveform; determinea desired amplifier class of operation according to the determined powerlevel; and control the amplifier to operate according to the desiredclass of operation.
 12. The apparatus of claim 11, wherein the amplifiercontroller is configured to determine a power level by determining aninstantaneous power level as a function of a desired output waveformenvelope.
 13. The apparatus of claim 11, wherein the amplifiercontroller is further configured to control the power amplifier tooperate according to a new class of operation.
 14. The apparatus ofclaim 13, wherein the amplifier controller is configured to control thepower amplifier to operate according to a new class of operationcomprises transitioning the power amplifier through an intermediaryclass.
 15. The apparatus of claim 11, wherein the amplifier controlleris further configured to: determine the instantaneous power level of thedesired output waveform; and control the power amplifier to operate inaccording to a new class of operation based on the instantaneous powerlevel.
 16. The apparatus of claim 11, wherein the amplifier controlleris further configured to: determine an average output power of thedesired output waveform; and control the power amplifier to operateaccording to a new class of operation based on the average output power.17. The apparatus of claim 11, wherein the amplifier controller isfurther configured to: determining the instantaneous power level of thedesired output waveform determining an average output power of thedesired output waveform; and controlling the power amplifier to operateaccording to a new class of operation based on the instantaneous powerlevel and average output power.
 18. The apparatus of claim 11, whereinthe amplifier controller is configured to control the power amplifier bycontrolling a drive level and a bias of the amplifier so that an outputcurrent conduction angle reaches a predetermined level based on thedesired class of operation.
 19. The apparatus of claim 11, wherein theamplifier controller is configured to control the amplifier bygenerating a pulse width modulated output signal.
 20. The apparatus ofclaim 11, wherein the amplifier controller is configured to control theamplifier by operating the amplifier in a switch mode.